Silversurfer has the right idea as not all screw sizes are the same, some are just different lengths, others have different diameters and/or thread pitch...

Find the size you need from the manufacturer and order them on-line. I've not had much luck finding them in any LHS or hardware stores, and if you do find them at the LHS they tend to be about 10 times as expensive as the folks Silversurfer mentioned.

Ralph is right concerning the Loctite, and I have to confess making a mistake when I said Loctite as I use Permatex brand where the color coding is a little more straight forward than the Loctite. In fact, there are so many Loctite compounds it can be difficult to determine which is best for a specific application.

And as for not using thread lockers on Karbonite gears, not only does Hitec not recommend them for gassers, but not for models over twelve pounds as well as the fact that if any of the threadlocker happens to get onto the gears it will deteriorate the material.