I have been looking for these for a while and I know others have too.
Found them on the Airheads.com site in the US.
Part no. N245281
I would post a link but don't know how.
Phil.
Lucky Phil ·
Aussieveedubbers · Tech Talk
5mm fuel clamps. Found 'em!
https://forums.aussieveedubbers.com/threads/96388/5mm-fuel-clamps-found-em