You can make plastic pants out of those small, white kitchen garbage bags. Cut the top off where it has the funny things you tie the bag shut with, then cut leg holes by cutting off the 2 corners of the bottom. Make sure you make them big enough but not too big. If you want to beable to take them on and off like you would a diaper or if they seem too lose around the waist, you can cut them down the sides right beside the leg holes so they open up like a diaper. Just lie down, position and pull the front up and fasten them with packing tape. Make sure you're very gentle with them as they tend to tear easily.
If you want absorbant material, you can buy some cheap towels from the dollar store and if you don't want to wash them, you can just throw them out with wasting too much money.