New steering wheel or seat would be quite costly if even available still. Check the Buy/Sell sections of this site and on mazdatrucking.com, and local parts yards.
If your interior is gray, and you're interested in a 3-spoke metal steering wheel, I have one available, from a B2200 and was formerly used on my own truck. Has center cap with original Mazda name strip (cap looks a little different than in this photo, that center cap is what mine has). Metal part has a few pits that might need repainting.
PM with offer if interested.
See