If by springy I think u mean a "manyard" - check out ebay theres always load on there or just google as loads of supliers have em.
does it have to be a double tail u need as if it helps ive got a couple of single miller baracuda lanyards left @ 1/2price & u could connent 2 the rear of your harness thats what we do if needing doubles for beamwork...the barracuda clap is far superior to the normal scaffolders hook