Pretty sure all of them come from Vintage Wiring, but can't prove it. Every once in awhile you'll find one on ebay but you run into the same problem of aged wire. You can convert an M35 front harness to the M38 and a1, but it is a lot of work. This option can be a lot cheaper if you find a cheap NOS harness to start with. You can prob convert an M151 harness also.
if yours is brittle, you might as well bite the bullet and do something before she burns to the ground! I am in the same situation myself - mine is very brittle and not all systems work as they should. A friend found an M35 (early, no turn signals built in) harness on ebay VERY cheap for me, but I haven't started the conversion yet. Wes has info and diagrams on willysmjeeps showing how to do it.
