Bruce gurgled happily, sounding much like they were
saying:

All the wheels offered by Towsure are either 100mm or 112mm PCD, which
neatly proves the OP's point.

I would suggest buying a modern wheel and having a machine shop drill
additional holes in it at 3.5" PCD.

A quick google on "4x90 PCD" comes up with Suzuki quad bikes as using
that fitment. It's probably a total red herring...