Hi Mike,...
To the best of my knowledge, Tascam/TEAC, Inc., is still the best source for these parts, service & stuff, of the 238, and all the other classic Tascams, up & down the line.
Tascam Parts dept: (323) 727-4840.
Of course, certain parts will be of limited availability, depending on type of part and age, but the 238's still modern enough that they'd hopefully have that kind of stuff.
AAMOF, I recently scored what appeared to be a near-mint 238, but it apparently needs a capstan motor too. Tape speed has gone all wacko, w/direct drive capstan. So, I'm in basically the same boat as you. I'll be seeking either a capstan motor, or Tascam Service directly, before too long, TBD.
No doubt, the 238, when working properly, is a super-nice unit, and I'm excited about my future plans of 8-in/8-out/8-simul recording to cassette.
Oops, sorry, 4-trackers!

Off topic!
Oh yes, 4-tracks & Portastudios, both things near & dear to my heart. I own a fair share of 'em, too.
JFYI, all you lurkers, catch lots of my 4-track Portastudio rantings at
http://www.nowhereradio.com/davemania/singles
-all classic rock covers, aka "Davemania".
