Elegoo actually has a nice and inexpensive product with the Vacuum pump & bag set. Unfortunately it has a serious design flaw which makes it practically useless.
If you try to suck air out of the bags you will always instantly build a vacuum with the back wall of the bag.

This little ring will help with that flaw. Either just put it into the bag or even glue it down inside the bag. From the outside place the vacuum pump on top of the ring and turn it on. Voilá.

I printed them out of inexpensive PLA with about 5% infill and 0.2mm layer height.