While there are "fitting" ESD bags, I had plenty of bags that were physically "too large" and have been bent over and taped to fit. So that really is no issue. If billion-Dollar-companies can do it, so can you.
However "3M and sealable" will cost a quite a bit. I'd rather use plain bags and an impulse sealer - if you are going for larger quantities. If only running for low numbers, maybe ask around at your local computer stores - at least we almost always throw them away (and that was likely a good 5-digit number of them).
Btw, by far the nicest bags came with IBM/Hitachi drives.