Don't know them directly but a quick google search turned this up;
https://socalporting.com/our-service...-body-porting/
If they can port them, they should be able to rebuild them as well.
There are quite a few shops out there that do mail-in as well.
http://maxbore.com/ That guy has a pretty good reputation and I've been looking into sending my KA throttle body his way when I run out of stuff to mess with on my S14. I'd call and talk to them about what you want done but I don't imagine either would have any trouble taking care of the seals.
Good luck, keep us posted.