Everyone probably knows this but I didn't and I am so excited I have to share.
I ordered a lovely new bag but it was patent. It's handles were also patent on metal rings.... SQUEAK SQUEAK SQUEAK!!
I melted some candle wax onto a sheet of baking paper so that I could lay it flat and then pick it up. Then rubbed with my fingers the metal rings all the way round the ring. That tiny amount of wax that actually came off and stayed on the rings made the whole bag totally silent.