Hi Fabrizio,
Welcome to zoochat. I can't remember how exclusive this particular arrangement is, but if you're after this specific form of eel ladder, it's probably worth contacting ZSL, or the UK's environment agency directly. We were told about this set-up in an evening lecture in 2010: Communicating Science: Conservation biology of the European eel - What's on - ZSL London Zoo - ZSL, so it might be helpful for you to try and contact the main speakers if you don't have much luck elsewhere. A number of companies do manufacture and sell eel ladders (like Milieu Inc., in Canada) but size of the eels, and the ladder, are important factors. I'd just like to clarify for anyone who may be unaware, that these ladders are usually used to by-pass obstacles along migratory routes, such as dams and weirs.
