UV filter + front cap: 40.5mm, 49mm or 52mm - SovietCameraStore.com
ZEISS T* UV filter 52mm - Foto Erhardt
Urth 52mm UV Lens Filter (Plus+) by Urth at B&C Camera
Amazon.com : B + W 52mm UV Protection Filter (010) for Camera Lens - Xtra Slim Mount (XS-PRO), MRC Nano, 16 Layers Multi-Resistant and Nano Coating, Photography Filter, 52 mm, Clear Protector :