While I had already designed a replacement key, I wanted one with a separate key and transmitter module. The module is just the remote transmitter.
Start with a Honda key with a cracked housing. Print all four parts, and add (6) M2 x 8mm long socket head cap screws, (2) M2 x 3mm long socket head cap screws, and (6) M2 hex nuts. There is a pocket within the head of the key to insert the anti-theft chip. The remote control door lock button housing fits within the fob.