I painted the inside of my brass Roxanne thimble with clear nail polish to make it grab a bit. Mine fits well, though. If you've lost weight, you've probably lost some in your fingers. Depending on how loose it is, you may be able to try a wrap of different things around your finger, like white medical tape (you know, the kind in the round metal donut) or even that brightly colored vet wrap being used around your arm after an IV or blood test. You can find that vet wrap at Tractor Supply, I believe, identical to but cheaper than the same stuff sold for humans in a drug store.