I got mine from Target. It's a curtain. Paid $15 for it, and it's awesome! I don't have the example in this pic, but you just buy a baseboard and clamp to the bottom of the backdrop. I have hardwoods, so I use my own hardwoods. I've also ordered some faux hardwood mats such as the PP posted. In addition, you can use linoleum flooring. It's fake hardwoods that snap together in pieces. You can get it anywhere from $15+ a box, and a box will make more than enough! If you need to lay it on carpet, I would suggest putting some plywood underneath or it will buckle. Same with the faux flooring.
Here is my damask
Here is an example of a seamless paper backdrop with the linoleum flooring
And lastly, here is an example with seamless paper, the baseboard clamped to it, and my own hardwoods.
Sorry if this got too lengthy!