Last January I bought a pack of generic stretch silicone lids. My hope was that one of the sizes in the pack would fit my 16 year old Snow Peak Trek 700. One did. This turns the mug into an excellent fuel transport container. It’s kind of a poor man’s Vargo BOT 700.
I have filled the mug with water, installed the silicone lid, flipped it upside down, and left it standing overnight. In the morning there were no leaks. I’m still hesitant to actually transport liquids using the lid. Mostly because the silicone is extremely thin, and I’m sure it is going to tear eventually. But if you’re into cold soaking food on the trail, and don’t want to carry a dedicated jar, I think this could be an attractive option. For leftovers, it’s perfect.
The lids I bought are no longer available, but there is certainly no shortage of equivalents floating around on Amazon-AliExpress-eBay. Based on the number search results, my impression is that China is drowning in silicone stretch lids.