I would have a look at startime they have added some bezels for the old gmt here is the links he sent me this morning i have a few coming so will let you know re case fitments etc once i try them on a few cases i have
http://store.startimesupply.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=1&Product_Code=RP316-16750&Category_Code=1D_Rolex_Bezel_Rotate-springs-bezelspring
And this bezel
http://store.startimesupply.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=1&Product_Code=RGBSS&Category_Code=1D_Rolex_Bezel_Rotate-Bezel-plastGMT