You may want to check with this gentleman. I'm not positive but, I think he's the guy that I bought a hood and wheel weights from last year. He has lots of garden tractors and other rusty stuff lying around and brings in more stuff from auctions. He was very reasonable too. It'd be worth a try.
You're a little far away. If I get desperate I'll start looking farther. Hopefully more people closer will see this post.
I made it out to Denton for the show. I only saw about 5 or 6 David Bradley walk behind tractors and not a single Tri-trac. It was pretty miserable this year with all the mud. A couple people told me that many people had left early that was selling things because of all the mud. I didn't see any David Bradley attachments for sell, so I'm still looking.