Found an alternative solution that lets me keep my current pump (hey, it works just fine!) but still toss out the 12v electrical system. But I’ve had to order the parts online since I was unable to find what I needed locally. It’s going to take a little while to receive it, install it, test it, and so on.
So I’m going to go out on a limb and say “I’ll open Monday, 16 October”. With the caveat “check here for updates if/when that plan doesn’t survive meeting reality”.