Try freecycle. It's a yahoo group and you sign up for your local area. Not only can you look to see if anyone is offering a crib, but you can post to say you are looking for one. I signed up for the one in the Shreveport area when I was living in Louisiana and I was able to find all kinds of things for my classroom. My sister in law uses the group in Omaha all the time for different things. All of the things on it are free all you have to do is arrange for pickup. I have found that often if you post you are looking for an item and make your situation sound really desperate someone usually comes through. You just go to yahoo, click on groups, find freecycle and go from there.
If you can't find crib you could always fold up a fleece blanket to put on top of the pad under the crib sheet. That is what we did when we traveled with our son once he got to be about 6 months old and could move around on his own. It just made him more comfortable and he was old enough that we didn't have to worry about SIDS. The other thing you could try in seeing if petsmart has one of those firm dog beds that aren't soft like a pillow but are more firm. I know it sounds weird to use a pet bed for your child, but if it was under the crib sheet no one would have to know. I thought about it for our pack and play but the pet bed wasn't as convenient for travel as the blanket. Good luck!