What are you looking for in a harness?
1. Factory fit/replacement or Universal fit?
2. Looking for a "kit", or custom wiring?
3. Is weight an important factor, IE Teflon wiring?
4. Cost can be all over the place depending on what you are doing.

First I would look at what wire insulation is being used.
Stay away from cheap PVC/GPT wiring. Look for cross linked polyethylene wiring, usually SXL/GXL/TXL wire. It can withstand higher heat, abrasion, and aging than GPT wire.

Might want to call Ron Francis Wiring?
http://www.ronfrancis.com/