Would be interested in knowing a good brand/retailer, I have one which I bought of ebay and using it on the Voigltander 50mm f1.1 its loose and not a snug fit, there are others on there but I dont want to waste money buying something that isnt fit for purpose.
Before you pan your current one, check and see if it has small slits (parallel to the mounting surface) in the mounting flanges. If so, you can ever so slightly separate those to tighten the fit.
Failing that, there's always the DMW-MA2M from Panasonic
