in all our tents we put down rugs,
here
here
just look for vintage kelims, vintage rugs, circler rugs, on ebay, go for smaller than the tent, you don't want to be touching the edges, you don't need them to go right out to edge either. over lapping small oblong ones work well also,
or go down to the local auction house, they come up a lot, I usually pay about £25 for them, a thin kelim does a brilliant job and rolls up to pack easily, they feel nice to sit on, we have a few old tatty persian rugs which are brilliant for camping, I chuck them down outside during the day for people to lounge on, last one to bed rolls them up, they last forever, as long as you make sure they are bone dry before you store.
I've managed to find round ones for all our bell tents, and yurts.
Ring the auction houses and ask them to let you know if any round ones come in.