RE: Polyurethane over Solartex?
If you head for the paint isle in Home Depot or Lowe's you will find a plentiful selection of polyurethane, both in brush or wipe on cans, AND in aerosol cans. Miniwax is one of the popular brands you will find. It comes in a gloss and in a satin clear finish, your choice. Best of luck and let us know how it turns out.... should be great. I know that lots of folks are using the spray to fuel proof decals, pin strips, et.
Ernie