http://www.dakkadakka.com/dakkaforum/posts/list/8.page JForum - http://www.jforum.net
I found this set on Amazon that look like they might do the job. One of the reviewer mentions Fimo and GS, and they're super cheap (plus I have Prime, so free shipping!).
https://www.amazon.com/COMI-Flexible-Sculpture-Silicon-Brushes/dp/B00MRTCP4G/ref=sr_1_1?ie=UTF8&qid=1487274882&sr=8-1&keywords=silicone+clay+shapers+green+stuff

There are other brands available in that price range as well, but it's hard to tell if they would really be too big for 28mm sculpting.

Any recommendations?]]> http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205287.page http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205287.page GMT
Size 0 are good for miniature sculpting. The heads are about 5-7mm long, and 3.5mm wide at the ferrule. Size 2 (7-11mm long, 5mm wide at the ferrule) are also useful for any slightly larger surfaces or sculpts, and then obviously, size 6 for the next step up. But I think size 0 is enough to go on for starters.

I have to say that I think even the black, extra-firm shapers are still a bit too flexible for most work, pushing congealing GS around, compared to a metal or wooden tool. Ditto for the fine points and edges that might be needed for tiny miniature details, being as they are, pieces of rubber on a stick. I tend to use them more for final smoothing and some subtle surface details, and for that I mostly use the round cup and taper point. But that's my experience, and I say play around with them to see what shapes you like and for what jobs. Especially when you get the whole wallet for that price.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205376.page http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205376.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205743.page http://www.dakkadakka.com/dakkaforum/posts/preList/718188/9205743.page GMT