Joey, some questions and then some suggestions.
What is the capacity of the receiver battery pack? How old is it? What is its capacity? Is it a nicad or nimh? If it's a nicad, have you ever cycled it? Do you test the voltage before you fly? Are any of your linkages binding (which creates extra work for the servos)? Do any of the servos make noise while you hold the sticks still, or when you move one of them to the maximum throw?

And now the suggestions:

It's not normal to have a battery run down in 9 minutes. If this is happening then you've either got a bad battery, or a nicad that needs to be cycled, some kind of short in the wiring, or your linkages are binding, which causes the servos to work too hard.

If you don't have one already, buy a battery tester. You need this to make sure the battery is fully charged before you fly. Use it at the beginning of the flying session and then before every flight. The brand does not really matter, just be sure you get one that applies a load to simulate the receiver and a few servos. A normal volt meter from Radio Shack does not include a load. Here's an inexpensive example of an R/C battery tester: http://www.towerhobby.com/products/towp1181.html

If the receiver battery pack is NiCad, you should cycle it a couple times. NiMH packs don't develop memory, so they don't need to be cycled, but running them through a cycle is a good way to test the capacity, and to know when it's time to replace an old pack. To cycle the battery you will need to discharge it. There are several ways to do this. The least expensive way is to turn on the transmitter and receiver and move the controls until they get sluggish. I suspect you have better things to do with your time, and it's not very scientific, so I do not recommend this method. Another choice is to hook the receiver pack to your battery tester. Using the battery tester requires that you watch it to see when the voltage drops off. You don't have to stare at it for the duration, just check on it every 5 or 10 minutes. You don't want to let it drain the pack fully. Another way is to buy one of the many products available for automatically cycling batteries. These are nice because you don't need to watch to see when the battery is discharged, they will automatically cut off at a certain voltage. The more expensive ones include a digital display to report the results of the test. Many of them automatically charge the battery after the discharge is complete. I'd rather spend my money on stuff that flies, so I just use my battery tester.

For information on the details of NiCad memory and the need for cycling, do some searches. There are many threads out there that explain it, so I'll be brief. Charge the battery. Hook it to your discharge tool of choice and time how long it takes to go below the recommended safe flying low voltage. Charge it again and repeat the test. If the battery was in need of cycling, you will find the second test lasts much longer than the first. If the battery is running down quickly after recycling it a few times, get a new one. Note, don't throw the old one in the trash, recycle it.

Next check the linkages to your control surfaces. You want all of these to move easily by hand. If they do not move easily then your servo needs to do extra work. This makes them use more power, and they also move slower. Also test to see if the servo moves to a point where the control cannot move any more. This will stall the servo and use a large amount of power. To test for this, move each control to the max in each direction. If you hear the servo humming, it may be stalling. If your transmitter has end point adjustments (EPA), use them. If you don't have EPA, you will have to adjust the linkages. Once you've confirmed that the linkages are working right, see how long the battery lasts while you are moving the controls around at home.

If you need to replace your battery, as tIANci said, consider buying a NiMH battery. They do not need to be cycled, and are smaller (and lighter). Since they are smaller for a given capacity, you can get a higher capacity pack (longer flying time) for the same size/weight. For example, the standard NiCad packs are 600-700 mAh. The same size/weight NiMH pack would be 1100-1250 mAh. The suggested 5 cell pack is not a requirement. The advantage of 5 cells is the servos will have more torque and will move faster. For the typical sport flier, the extra speed does not matter. If you're doing 3D or other competition, the extra speed helps. The disadvantages are the extra cell makes the pack a bit heavier/larger, and the pack will run down a little faster. The discharge rate of 4 cell versus 5 cell packs has been the subject of much debate, hopefully another one will not start here. If anyone is interested, look for some of the threads that have beat the subject to death.

There are many online sources of batteries. Here are a couple:
http://batteriesamerica.com/
http://www.hangtimes.com/nobsbatteries.html
I don't think there is any reason to look for a car pack. It's easy to find receiver packs with the appropriate connector already installed. Sanyo cells tend to be highly rated.