DIY真空袋

Print one of each. If you want to make multiples, you only need the main body, nut, and bolt; the trim ring you only need one of to trim your plastic bag.
Get a zip-close type plastic bag, slip a piece of cardboard or something hard iide of it, roughly center your trim ring on it. Take a sharp hobby knife, cut the center section out and set it aside; then cut the outer perimeter. Throw away the "ring" part. Slip the main body up iide the hole from iide the bag and poke the threads through. Slip the nut on and tighten down. Get the center section you set aside a second ago and push it down in the middle, cut a hole in the center so the bolt can go through. Put the bolt through and tighten. I cut a slot in the bolt that should be just right for a US quarter to tighten it so you don't need any tools.
I came up with this so I could make one for each bag of filament to vacuum pack it; originally I had contemplated putting a bunch of rolls of filament in one container and putting desiccant in it, but every time I'd open it, it would let moisture in to all the rolls. By using single bags per roll, you only risk the one roll you open at a time. Run the filament through a dehydrator and put back in the bag with desiccant, then vacuum. (I live where it's humid a lot of the time so for me this is critical.)
I have an inexpeive ($10 US) air bed type inflatodeflator that I measured the inlet for; it's tapered but it looked to be a good fit around 30.5mm so I made the iide diameter of the main body that size.
Note: I have not tested it! I suspect it might need a light coating of some silicone over the areas that need to be sealed.
Update: 9/25/2018 - I added a tiny bit of clearance on the threads as I suspect they'd be too tight. I also printed them out, my printer is underextruding a bit so they're a bit ugly, but the threads fit perfect.