I have a 90 f6.8 Angulon lens in a Linhof Sync Compur shutter. Shutter and lens is in great cosmetic shape but one of the diaphram blades is hanging. Anyone hav e a recommendation regarding who can repair this shutter at a reasonable price? If repair is too costly I plan to purchase a used Copal # 0 shutter. Who sells u sed Copal shutters?