Ha ha. Last week one of my collets flew across the shed and despite extensive searches has not been found. Tat's when I discovered there were none of be had anywhere. I needed spring retainers too so I got a set from SRM, £65 for 4 collars and a matched set of collets which compares favorably with the £40 for just the collets. SRM use different collets so that's why they supply the collars to match.
After seeing that price I'm going to look even harder and list my old collets on e-bay. If you see 7 for sale you'll know I never found it