adding a second ceiling fan remote

I installed a Hampton Bay ceiling fan remote, and now I would like to add a second remote control transmitter to keep in another part of the room. I know I can just buy another complete unit, set the dip switches on the transmitter to match the installed one and just discard the extra receiver, but that seems awfully expensive to pay for the whole thing when I only need the transmitter. Does anyone know if just the remote control part can be purchased, or is there a universal remote that will work?
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