Hi handson,
Just a quick question first: why do you want a footprint for the Hubba Hubba? Reason I ask is that I have this tent, & it's been a good one for several years. I bought myself a footprint a couple of years back, and use it occasionally -- when I'm using the tent without the inner mesh tent to protect me from the bugs. So, I use the footprint (here in Eastern Ontario) in the spring & fall, before & after the bugs. I bought the footprint for a couple of European journeys, a hiking trip in the Spanish Pyrenees & a cycling trip from Amsterdam to Vienna. Worked fine in both -- amongst their other delights, neither trip had any bugs. In both cases, we were two inside the tent fly, and not having the inner tent made it much roomier. (Ventilation to limit condensation became a little trickier, however.)
When I use the inner tent (the default mode), I use a sheet of plastic, usually 2 mm (sometime 4 mm, depending on what's available), cut to 5' x 7', to protect the outer floor of the inner tent from abrasion.
You may have trouble finding just a footprint, if you're looking for a used item, but I'd check on e-Bay, kijiji or craigslist, etc., plus gear sales at outdoor stores in your area.
Hope this helps in any case -- good luck.