There are a few products out there to add one to your BX but not cheap, or you can buy a bolt on thumb and like Garyoc posted above and then fabricate a mount for it on your FEL, then figure out how to add a third hydraulic circuit to your FEL to control it. Do a search in the attachments forum for "grappleomatic". Member Artisan posted a very comprehensive thread on how he added one to his BX25 and I think there's links to other products/options in that thread.