. . .<snip>. . .Apparently, from talking to other Aussies about it, a well stocked bearing supplies outlet should have stainless steel sealed bearings the correct size. . . .<snip>. .
That is exactly where I get my new bearings. I just took the old one into the bearing supply store and threw it on the counter. In less than a minute the guy walked back out with the exact bearing. The didn't have the stainless bearings in stock, but ordered them for me within a week. (About $10 cheaper than Boca)
You can stick your ear down by the spinner (Glow plug disconnected!!) and slowly rotate the prop between compression. If you can hear anything, the bearings are going. You are correct - some guys bearings last hundreds of flights, while others last just a few.
The common thread seems to be heat. Make sure the rear of your engine gets PLENTY of cooling air. I've seen some guys go so far as to create an air scoop surrounding the whole spinner. The hotter that the rear bearing gets, the quicker it rusts.
If you need to know how to change the rear bearings, PM me and I'll let you know how I do it in about 20 minutes.