Pyramid Air has the Air Venturi Single Shot Tray for the Gamo Urban and BSA air rifles. Cost is $19.99.
http://www.pyramydair.com/s/a/Air_Venturi_Single_Shot_Magazine_for_BSA_Gamo_PCP_Air_Rifles/8798
http://www.pyramydair.com/s/a/Air_Venturi_Single_Shot_Magazine_for_BSA_Gamo_PCP_Air_Rifles/8798