I've got a super old, but much loved Brommie - it has the 6 speed SRAM 13/15 sprockets. I've just changed my chain and want to change my sprocket set (for the first time). I'm looking for a brompton sachs/sram 6-speed sprocket set 13/15 but most places have sold out. Does anyone have any idea of where I could get hold of older parts for a geriatric Brommie?