Which generic harness is less expensive than $150?

The $150 Classic Parts plastic-coated harness is a year-specific harness. It uses the your original fuses/breakers. Jim Carter sells a similar harness.

generator harness and alternator harness

They used to provide enough additional different colored wiring for add-on signals. If you want signal-lamps, you might want to call to see if this is still the case.

If you want more circuits or want to use non-original circuit-breakers and/or fuses, a generic system/harness is what you might want to use (and, you will have to measure/cut/terminate wires).