Bulb Pump for Belly Inflation

I think you can just buy a bulb pump. Though I wouldn't know exactly which department that would fall under, I'm almost certain that you don't actually have to build your own.

I've made a lot of these devices over the years.  You can get a bulb inflator for sports balls at the sporting goods store.  But don't start there, go to a cheaper store that would have a sporting goods department like walmart or any cheap store.  So when you find the inflator it usually has a valve on it just like a blood pressure device, and a pin for inflating the balls. Unscrew the pin and put it away til you need to inflate a ball.  See if the hose will connect to your device you use.  If not, you can buy flexible plastic tubing at a hardware store or home depot.   If you get several different sizes of tubing you can find ones that will stick firmly on the end of the inflator.  You can use several different sizes of tube stuck together to make adapters to get it to the right size you want.  The pulsing of the bulb feels different and is a good feeling.  You also have a little more control of the speed of the inflation.

I bought one at a dollar store that is used for inflating a basketball. I just unscrewed the needle attachment, and put the tube in its place. The tube was a bit too small, but some duct tape did the trick. It works, but the pump isn't very powerful and takes too long to see any sort of bloat. I prefer using a hand pump used for inflating bike tires.