Jaka, there are currently 2 bladder tanks on the market in the US that I am aware of. Dub Jett sells his line
Dub Jett model aircraft - Bubble-Jett fuel tanks and accessories and the Tetra tanks that are available from Darrol Cady
Darrol Cady > R/C Model Aircraft Tettra Tanks. I have used both and have found no performance difference.
Scott