Carp Fishing Tackle and Coarse Fishing Tackle from Total Fishing Gear. TF Gear's website is packed with fishing equipment offers, with online mail ordering.
www.totalfishinggear.co.uk
I doubt the spring will be an unusual size , shape or compression type so a center pin maker such as J W Young and son should be able to help. You might need to buy a variety of sizes if they do vary to get one that fits but worth a try. Small springs can be bought of eBay and Amazon.