Could you get some under size and put another roll pin inside to spread it outMeasured said ole and it’s about 7.5mm. Couldn’t find M7.5 and was too lazy to convert it to Albanian parsecs so got M8 and will use a bigger ammer to drift them in. The good news is they’re stainless.
Oh now you come out from under your rock5/16" spring roll pin .... https://www.britishpipeclamps.co.uk/product/imperial-spring-pins-steel-516-x-2/