I don't see why any competent machine shop couldn't make these
U-bolts for you, using either threaded rod or rod the same diameter
cut to correct length, threaded at both ends and then hammered over
to form the u-bolt profile.

If you are skilled enough you could do so yourself, and use brass rod
instead for easier going.  I will grant you, the 8-32 thread is fairly
small to match but it can be done.  All a shop would need, would be to
borrow an example.  You could then give them and order large enough to
give yourself a few spares.

Congratulations and Good Luck on your project!

Tom Detweiler