Hi. I got some 0.5 cro ox from thiersisard.co.uk for £20 they also do thiers issard diamond paste but its quite pricey. They do their own diamond paste too which is cheaper. Steve Dempster whos the vender also has sister sites dovo.co.uk and the invisible edge. Ive brought loads from the sites and he also hones and restores. A great person to do bussiness with.
Neil Miller at stropshop.co.uk does diamond sprays which are about £12 which Ive also used so you cant go wrong with either. Neil also makes his legendry strops too. Ive got his bridle leather with natural linen which is beautiful to look at and use. Many people on this site has his strops and can attest to his craftmanship.
Good luck