Where do you live again Darkmessiah? If you\'re in the US there are plenty of things you can order online that might be suitable. Come to think of it if you\'re in the UK the Sterling is so strong these days that you could have something shipped directly to you and still come out ahead.
If you want go the microballoons route get it in places like
here,
here and
here, not from a hobby supplier repackaged in small amounts and priced through the nose!
Other things to consider:
alum;
Cabosil;
hydrated alumina.
Marble dust is sometimes mentioned too but it doesn\'t really work that great for small-scale stuff (looks best in the coarser grinds, which look OK for large scales only).
Einion