This one doesn't get great reviews, but the size is right. https://www.amazon.com/UNDERBED-STORAGE-BAG-ZIPPERED-ORGANIZER/dp/B000GULUMG

Here's another option.

https://www.target.com/p/clip-storage-box-green-sterilite/-/A-14758436

I don't think any rigid plastic storage containers are less than 6" high. The zippered, plastic, collapsible containers are the only type that are less than 5" high. Here is ONE. Few of these are very large, however. If you need to store coats or dresses I suggest you buy a zippered garment bag and seal the hanger slot at the top with duct tape after you have packed your clothing.

I have only visited Ikea ONCE in my life - a month ago - and they had a good selection of under bed drawers! :)

This under bed sweater bag gets good reviews for those with low height beds because you can squish it down. I'd think you just wouldn't want to pack it jam tight so there is some ability to squish it down.

https://www.containerstore.com/s/closet/under-the-bed-storage/peva-under-bed-storage-bag/12d?productId=10035434

Clean Clothes in space bags and then in containers with lids that seal.

You will for sure need to use the sucky bag first to get anything into a 5” box

Why no risers?

Space bags and alike do not stay. Trust me, been there...done that...with all the different brands.

Eventually air leaks out of them.

Not so much fun when you slid them under your bed, and now they are TOO poofy to come out. :)

I second Jora; NO on space bags.

You might try looking for low profile or shallow gift wrap storage boxes. I found one that’s zippered fabric, right at 5 inches high:
https://mdesignhomedecor.com/fabric-gift-wrap-wrapping-paper-storage-organizer-box/?gclid=EAIaIQobChMI2Kjh64Cq5AIVCoTICh3ILQNlEAQYDiABEgK2wfD_BwE

@jora I’ve used space bags for years and never had them leak (had them sit in storage for months to years depending on what’s in them) ... maybe you overfill them? Don’t suck enough air out?

I honestly just can’t see what you could store in a less than 5” deep box or bag. I dislike under bed storage since every time you vacuum you need to pull it all out I would look at adding some good organizers in the closet.

Karin - Never have overfilled them, always sucked all the air out. Everything looks fantastic for a few weeks, and then BAM. I can not tell you how much money I've wasted on these bags. I will never use one again, even if it was free!

And on the same page as Patricia...just not a fan of storing things under the bed, UNLESS it's an actual under the bed drawer.

We JUST purchased an IKEA bed with storage (was an IKEA virgin before), for the guest room. Couldn't; be more in love. I've managed to fit all the extra sheets, blankets, and pillows in the four drawers. IT'S FANTASTIC!