I'm actually quite lucky in that my husband knows a guy who does upholstery (and well). I've picked out the vinyl and he has the foam, but we're waiting to shape and cover it until I have a rolling chassis so that he can fit it proper on the bike. He said he'd just charge me for the materials, and he's going to let me help. I think it's going to be less than $100 all said and done.
On another note, I managed to source front and rear spoke sets and have the wheels at the shop to have them laced and new tires installed. I'll likely be taking the motor to them too for new crank bearings and seals, etc.