I'd bet there are LF photographers here who'd send you one.
Another option is a paper safe. Relatively inexpensive, and light tight. But yes, those bags you linked above look reasonably safe (and the labels are a nice touch). Don't rolt them too tightly, so the film corners don't poke through. I've never unloaded my film holders without being ready to process, but if you have more shooting to do (on vacation, for instance) than you have film holders, this could be a good way to go.