[Don Plumley]

There's a big dismantler in DC area: DC Auto
I've seen an ad for one in Oklahoma: Oklahoma Foreign
Parts Haven in Hayward, CA
There's one in Georgia that the rep is not very good

I bet the cost of fixing the gear is an order of magnitude cheaper than replacement though.

If you get from a private seller (track guys will often have their old tranny when they upgrade), consider shipping it in a big cooler.