I think making your own pump - the actual pump, is a lot harder than it looks.
For the purpose of a penis pump we don’t need to move much air, low noise is preferred and a maximum vacuum of 15” Hg is adequate - these requirements can be met with a $20 diaphragm pump readily available on the internet.
I have been experimenting with electric pumps for a few years - see my other posts for details. A couple of my pumps are diaphragm design and they seem to work best for me. One is the aquarium air converted to vacuum and the other is a small 12 VDC pump I found on eBay. I also have a 12 VDC piston pump (another eBay purchase) which displaces much more air (creating vacuum faster) but it is noisy and is prone to sticking when cycled on and off regularly. The very common Medela Lactina breast pump uses a piston but is quite expensive even on the used market.
I suggest you consider 12 VDC instead of line voltage (120 VAC). This opened up lots of new possibilities for my designs. There are lots of cheap timing circuits, relays and digital pressure gauges that all work off 12 VDC as well as regulated power supplies to convert line voltage to 12 VDC. Another possibility is 12 VDC battery based systems if portability is desired - look for Li-ion rechargeable battery packs of about 10000 mAh.
Let us know how your project goes!