I've been buying similar fasteners from J Clarke Marine (
https://www.jclarkemarine.com/). Typically on ebay, because it's so ridiculously easy.
Their very speedy service and quality have always impressed. Speed especially since they are in Northern Ireland, with that extra water to cross.
(No link other than a satisfied etc.)
I'm sure Woolies Trim are good too but I've yet to give them a try.
