When I picked up my used Bachetta Belladare (your Bella's older brother) at the dealer in Seminole, FL, I picked up a Bontrager wired speedo for it, with a LONG harness. It was about $20 or so and has been working well. I have tried wireless computers on a couple of different recumbents over the years, and have not had great luck with them. I can't recall the model number, but it ended with an "L" (for the long wire).

Tractor Tom in Okeechobee, FL