Maybee put a matress or something in there to put against the door.....
Companies donate NEW kids beds and stuff to goodwills and salvation arm stores and then like that (tax write offs). So you could probally get some kind of kid mattress for like 10 bucks somewhere.
If you can't find one maybee use a heavy sleeping bag or something....
You could probally buy a new kids matress for 20 or 30 bucks somewhere.
If none of that works, try to find a used futon or something somewhere (consignment shops, flea markets, yard sale). Spray the mofo down with some disinfectant first though. Even with the disinfectant, I would still be worried about head lice and shit..... I'd call the used matress the last resort....
Sorry that none of theese are very "pro" solutions, but I tend to just wing it myself.