Does anyone know where I can purchase MT 2001 couplers that are pre assembled? I have found the 2004 assembled, but I need the 2001 long shank. After 3 hours I have managed to assemble 1 of the 2001's. It's not that I lose the spring so much as I cannot get it to stay in position while I snap on the top piece so I end up damaging the spring. Thanks!