Greetings from Asheboro!
If A&H washing soda is difficult to come by, an accptable alternative is Cascade (or similar) dishwashing detergent. I have restored 5 vintage woodworking machines and electrolysis, utilizing dishwashing detergent, was used for all de-rusting.
You can also make washing soda by baking regular baking soda at 300 for an hour or so to drive out the moisture and carbon dioxide. It's a common practice for saltwater aquarium people. And it will be higher purity than laundry washing soda. Overheating or heating for too long is not a problem.
(What's goin' on my man, how's life in the Queen City?) I have used Cascade w/ good sucess, I think it just takes slightly longer than pure washing soda.
I actually have a pretty decent electrolysis tank set up for restoring "vintage" tools that you are welcome to use if you're not in a huge rush. I imagine we'll be getting out that way at some point to visit a few of our mutual friends sometime in the near future.