I got my odor barrier bags when they were sold as Nylobarrier Bags by Litetrail. I believe that they are now available as BaseCamp Odor Barrier Storage Bags. Disclaimer - I know nothing about this retailer. I just Googled to find someone selling. But just like the package sold here, I got a sample pack of 2 large and 3 medium bags. My large are the perfect size for a pack liner and the medium are the perfect size for a food bag liner. I use one of each. This puts two layers of odor barrier between my food and my sleeping bag/clothes when everything is stuffed in the pack. I can say that before I used these, when I opened my pack after a few days on the trail, everything smelled of the past week's breakfast, lunch, and dinner. But now, my pack is noticeably less smelly. I'm not sure they are not strong enough to use alone as a food bag (I have a Zpack Blast Bag). But as a liner they work great. I have been using the same liner for several trips and they are still air/water tight. They don't have any seal - just an open bag. But they are large enough that I take the neck, twist and fold over to keep odors in and water out. I am not 100% sure these are the same bags and the same size, but I have read on-line that they are and as you know, everything on the Interweb has to be true.
https://www.summitracing.com/parts/bcp-f232335