creative plant sign holders

I'm trying to come up with a more eco-friendly way to protect our plant signage in the research gardens than lamination. Sheet protectors work for full-size signs (though only for a while, they UV degrade), but most plant signs are going to be 1/2 sheet or even 1/4 sheet. Someone suggested badge holders, but the biggest I find for them is 3"x4", which is a little too small. The signs are going to have pictures on them as well as text, so half sheet (8 1/2" wide x 5 1/2" tall) would really be best. We'll probably have to run a strip of clear packing tape over the opening on whatever we use to protect the signs a bit from moisture, but that's better than laminating the entire thing.

My ideal would be something durable (doesn't UV degrade) and reusable. Trials typically only run for 3-5 months (say May - Sept), so these aren't permanent plant labels. I love the idea of badge holders, if only I could get bigger ones. Hmm, don't runners wear fairly big signs? Maybe too big, those are probably full sheets.

Suggestions welcome!