Ryan, i do not know of any used ones for sale but i bought one of the ez ski trainers from overtons and had my 18 month old riding in no time this summer. It actually comes with a handle you hold from the boat and you can let go of it if they fall (rope is approx 50ft). the bottom part is the same structure ski in your picture and the top part is inflatable. the extra handle also works great for starting them out on the shore. Dont know how old your nieces/nephews are but if they are under 2yrs then the ez ski is the only way to go imo. hope this helps
Last edited by jrich; 08-21-2012 at 8:12 PM.