Hello,
I would try going on ebay for a low cost play pen which will give him room to move around and potty. I would put this in the search.
2-Door Soft Playpen Dog Crate Cage Kennel 36"x36"x24"H I have one of these and love it because it allows me to put Couture in it when Im in too busy to keep a close eye. I would still get this even if you have a crate it portable and has a bottom liner that keeps the floor dry even if they potty and its washable. I even put my baby in it when I cook outside, considering that she cant touch the grass yet due to waiting on her last vaccines.
I hope all this helps and good luck! If you need a little more help feel free let me know.