I'm confused whats so bad about your tent??? It looks like a legitimate tent. I'm also confused whats so wrong with wanting a footprint for it.
It all depends on how you want to make it. You could go from super cheap to super over done. A trash bag can be cut up to shape, or tyvek is very comonly used. Eureka sells 6mm polyethelene. Just cut and be done with it. Most footprints are made from waterproof materials. 1.9 oz coated, either taffeta or ripstop for lightweight or oxford for the heavier but sturdier. Get the correct dimensions with a trashbag/tape or newspaper/tape and copy the pattern. Some grosgrain ribbon on the corners for stake out points, a half inch seam around the edges and instant footprint.
You could make it such that your fly and poles could be set up with out the body. The problem with this will be finding buckles that will fit. Good luck with that. You may just have get new set of buckles and attach them to the webbing on the fly and switch them out depending on how you are using it. Not being familiar with you tent, you are going to have to figure out the details (how to attach the poles and dimensions).
Any specific questions?
Scott
Oh and check out the eurkea site, they only make square and rectangular footprints, so any shaped tent has to cut them down to fit.