Don't know how I missed this...
In addition to the 4 T. maximas left, I've also got three T. derasa clams that are right around 3.5-4" or so. They've put on a half inch in the 6 months I've had them; you can see the new shell growth.
Two of them are pretty nice and I can let one go for $45, one is not quite as nice (though it should color up, as they're all from the same source and I think it's just in a slightly worse spot) I can let go for $35. All aquacultured.
Derasa clams do best on a sand bed and do well under less intense lighting, whereas the croceas and maximas prefer to be on rockwork and need high light levels.
Let me know if you're interested and I can bring one with tomorrow.