Re: I know I saw it on a web site once...

Glenn, I think you are in the US, but if I've erred...

http://www.geohex.com/ftssbwt1.htm
has packs of 4 bases, I think the metal ones, for $7.50. I've had better
luck finding bargain bin ship packs, especially scoutships and
corvettes,
and use some of bases if I don't need all the ships. I think KR has
plastic
available, also, but you may have to ask him directly.

Dream Pod 9 has plastic 'flying bases' on their Jovian Chronicles site:
http://www.dp9.com/Products/JC.htm

GW has many and varied plastic bases, but I consider them mighty pricey
and
I have trouble with the plastics being brittle.

A walk through the archives should find plenty of suggested alternatives
to
purchased bases, though.