I have used the stick on weights that Tickle has posted the link to. Stewart Lister gave me some to try at the Dynamite Baits festival last year.
They are the business. Stuck one on to a drennan cage feeder then and am still using the same one now – it has never come off. But do ensure you stick it on carefully, and that the surface is clean and dry. My bro tried it in the rain and had problems. Basically, I polished the exisiting lead strip on the feeder when at home, and stuck one of these on top. I always have some in my box now.