For the purposed of the original poster, he would be well advised to
salvage a sealed compressor from an old air conditioner or
refrigerator, then convert it to a vacuum source per article that both
appeared in Scientific American and the Amateur Scientist's Handbook.

I think its much easier to buy a pump vs make a pump. There
are plenty available. I think the conversions centered around
belt drive AC compressors, which I think are a thing of the past??