Visited Towsure in Southampton yesterday and found they sold the fluid for minor leaks to rib tubes. They had four bottles on the shelf, they now have 3
Cost £11
They have a website and quite a few dealers so might be one near you. They also sell lots of other marine stuff cheap.
http://www.towsure.com/
The fluid is made by Polymarine,
http://www.polymarine.co.uk/pm/
Pete
