Actually they aren't sold. Pinfiring is used to speed up the healing process to get them back on the track quicker. Why would they waste money trying to heal a horse via pinfiring to just sell it? That makes no sense.
Many many many horses are pinfired, it's not illegal in Canada as far as I know, though the process is getting outdated as AlmagroN explained.
Which vets have you personally called up and talked to?
It is now illegal in this country, I'm pleased to say, and I imagine it is in most countries although the method will still have its proponents, I'm sure.
And the address to the writer is
8262 Coldwater Rd.
Stokesdale NC, 27357
I've talked 2 my local vet about it.