I stumbled on this looking for generators. It’s the electronics for a Harbor Freight 9500 generator. Seems like a reasonable price for a backup.
https://www.amazon.com/Tapa-Inverter-Predator-Invertor-Generator/dp/B0B6R3MXVL/
Here’s the rotor and stator:
https://www.amazon.com/dp/B0B6R63CN3/
There are some reviews that seem to say this could be used on Harbor Freight’s open-frame inverter-generator. I wonder if that means they can be paralleled?
edit: I guess you can, sort of: DIY Predator Parallel Kit - #5 by Matt