Go to the Links here and you'll find several....and different prices! With what your suggesting 12 circuits would work but you can find harnesses with more circuits for about the same money.
Personally, for value to dollar, I like Rebel and EZwire. Rebel wire was giving Bolters a 15% discount off their already good prices..... however, I went with EZWire as I wanted the "mini" fuse set up.
Lots of options out there so put on your reading glasses and get started

Say, how about a picture of your 37 when you can get to it.