You need the gasket kit which includes rubbers and tiny copper rivets – do not lose!
Drill the heads off the old rivets, prise apart the bailer and replace the rubbers. Replace the rivets with new and peen over the end that hasn’t got a head with a steel hammer. A centre punch helps to start them. Make sure you get everything snug. It is the same as you do with a traditional copper boat nail and rove.
The price of the kit is very high and only just justifies not buying new bailers. I replaced mine last year (using the kit) and the rubbers supplied are not 100% water tight so they still leak slightly. If you buy new bailers you could at least hold them up to the light to see if they’re watertight.
I hope this helps – it is not difficult but a bit of a fiddle – don’t lose the little rivets when you open the box!!