Ebay has a lot of great options! One thing to know about sissy bars and banana seats is that when you are shopping for them you will see ones that are marked as 16inch, 20inch, and 26inch. These numbers do not denote the length of the seat, but rather, are an indicator as to which size bike the seat will fit with based on the size of the wheel. So if, for example, you're turning an adult size beach cruiser, or old mountain bike, into a banana bike then you would want a 26inch seat.