99 4-Runner Converter

Recently I went to rent an RV trailer and discovered that my trailer wiring harness (Toyota installed with the hitch) didn't function. Wound up using a borrowed truck. However, when I took my runner to a local dealer I was told that the converter was shot. I figure, no big deal. Wrong. The tech tells me that when you order one from Toyota you have to get it with a complete wiring harness. That's gonna cost me $300 plus, not including a few hours labor. I'm disabled enough that I can't crawl around the guts or underbody of the runner and "have" to have someone else do it for me. Searching a junkyard for electronic components doesn't strike me as a good move. Can anyone suggest a cheaper alternative? I have to be able to use a trailer because we live in the country with no garbage pick-up and I need to haul my own trash to the dump each week. I'd appreciate anyone's input. Thanks, Mike