YnZ Yesterdays Parts https://www.ynzyesterdaysparts.com/
They offer additional options such as turn signal add on wiring, or not depending on your needs.
I ordered from Tyree recently. Great service and a good part, too. I like supporting the little guy, the independent. My family survived on a small business income.
Bauer Electronics fabricates them for several different parts sources. They are decent quality and come with good instruction sheets. All model A harnesses are pretty much the same with exception to some AA trucks due to frame lengths and tail light distance from the light switch. Some have better light switch terminal discs than others. Rhode Island Wire likely makes up the best quality harness but they will likely be a bit more expensive too. They coat the fabric wire covering with a clear coat to keep the color longer Bauer doesn't coat theirs.
Bratton makes a very good harness, with all the connector ends being soldered, as opposed to Snyders that has clip on ends and no solder in the harness.