Fossil squid do sometimes come up for sale like this; one major source seems to be Jurassic Solhofen deposits from Germany. This is a site of excveptional preservation and the source for the seven verified fossils of Archaeopterix, the infamous dino-bird. Some European fossil shops occasionally stock these squid but prices are usually at least $500 or more depending on the state of preservation, rather too expensive for me!
It's worth keeping an eye on e-bay as this was certainly not the first specimen of Trachyteuthis to be advertised here. Perhaps a cheaper one will sneak through one day!
Clem, what on earth is your new avatar? I can't make head or tail of it?
If anyone is feeling rich this month here is another beautiful example of Trachyteuthis libanotica for sale. This Cretaceous squid was probably a vampyromorph. The soft-bodied preservation on this example is fantastic.
For the record, I've just found out that Trachyteuthis is not believed to be a vampyromorph but belonging to the mesoteuthids, a group that split from the vampyromorphs in the mid-
Jurassic and is now believed to be totally extinct. They were not the direct ancestors of modern squid at all.