Homemade inflatable butt plugs for under 50$

Does anyone know of any ways to make a cheap but really good inflatable butt plug?

Inflatable butt plugs only cost $30.

Inflatable butt plugs only cost $30.

Yup. Gone mainstream - Amazon has a good selection of them, with free two-day shipping!

The best homemade plug that made was from a punching balloon set and a blood pressure pump thing. Put the pump up to a small metal cylinder that would fit into the bottom of the balloon and tied it with a zip tie. All that's left is to clean out and lube up.