Hellobee Boards

I have some under bed size from container store that zip - I like the little bit of built in structure though still a bag. Container store is definitely my go to for oddly sized storage needs! We have some of the sweater bags also but I find a smaller size less useful unless you have a ton of closet shelves or something.

I have both the ziplock and Target's Room Essentials brand vacuum bags. Both have worked well for me over the last 4 years (and I've repacked and emptied them a few times). I put the bag in a clear storage tote and then vacuum out the air pressing down so it takes on the size of the tote. I usually fit two bigs in a tote and stack them up in storage that way.

ETA: I've also liked IKEA's under bed storage options:
https://www.ikea.com/us/en/p/lackisar-storage-case-30460929/ https://www.ikea.com/us/en/p/skubb-storage-case-white-60300048/