Does anyone know of a reputable vendor that provides sleeves to allow you to use various sized batteries with different mods? I have one that will allow you to use an 18650 in a mod designed for 26650's, and I started looking around to see if there is a vendor doing this. So far I only found some cheesy stuff on E-Bay with bad reviews. The thing I have is a Delrin tube and it seems to work really well. I'm usually pretty good at finding what I am looking for via search engines but no joy on this one. Is this just not a thing?