Just spotted this...
Kitchen Floor Vacuum Former -- uses a standard shop vacuum.

Best bet is ask frankd20! He has built and experimented with DIY vacuum forming machines! I guess if anybody knows, he would! Check his Workbench Creation! Big it up for Frank

Use whatever vacuum you have, a medium duty shopvac 5.5hp is ideal.

I've included some pics of a former I made, with the vacuum it will handle at least 1/4" plastics heated properly. The oven is the tricky part, don't want to ruin your kitchen oven, find a used toaster oven (if it handles your size requirements, not sure as your info was limited "Guest") and creatte a frame to hold the sheet plastic.

Construction:

2 Pieces of 5/8"-3/4" wood cut to desired size 15x10?

1 Piece of 1/4" wood frame cut to matching size, 1.5-2" border.

1/16-5/64" holes drilled into one of the 5/8-3/4" in a 1x1 pattern leaving the 1.5-2" border.

Drill the desired size hole in the other 5/8-3/4" sheet for pvc piping (to match your vacuum). attach a 90deg. pvc elbow to the sheet, and piping to interface with vacuum.

Glue them together clamp them down, seal the sides and attach desired stand structure and your ready to go.