I made my own. Bought one for a cage at Wally World, laid it on my bike seat to determine the size and shape, then cut the nylon strings in the appropriate areas and started removing beads until I got the size and shape I wanted. Then I threaded an .080 line from my weed trimmer around the perimeter to hold it all together and presto, I had my custom bead rider. I did it mostly for something to do in the garage one rainy day and am happy with the results, however I very seldom use it. Cost me about $10 instead of the $30+ the bike specific ones go for.