Not exactly sure what you mean by sides going down all the way to the floor.
If you don't find the desk you like from places like Ikea, Amazon or other places... you can always go to Homedepot and build your own. I did just that. I wanted my son and I to be side by side when we're gaming. I couldn't find a desk wide and deep enough. I wanted it to be also in one piece. I wanted a carpet surface to not scratch anything when I fix things on the table. I bought the widest Ikea table and I put a big piece of plywood, about 3' deep and 8' wide. I'm extremely happy.
All I used were cordless drill/screw driver, jig saw, box cutter and a hammer (for the tacks to hold the carpet in place). Desk was $90 and materials were another $40.