Low-cost Talon SRX computer?

[GeeTwo]

As an off season project, I'd like to lead a build of a couple of the catapult concepts we had back around week 1 or 2 that we dropped because we didn't have any experience with them. Ideally, these would be standalone projects, with no drive system and a low-cost controller (e.g. arduino, rather than RoboRIO). One is essentially pneumatic, so we're ready to drive this with some relay modules. Another requires PID. I don't see any reason that a Talon SRX internal PID shouldn't fill the bill, but I really don't want to commit a RoboRIO to control the SRX over CAN. As controlling the SRX is a means rather than an end (our end is more mechanical), I'm hoping we can adapt a relatively inexpensive way to control an SRX via CAN. Arduino would be the preferred tool, as we have several Leonardo clones already in hand, but learning another infrastructure if needed is certainly acceptable.

A search for CAN bus shields turned up a number of shields with DB-15 ports to interface to vehicles. While this may be adaptable to our needs, it was not clear from a high-level read of their capabilities. I also found a number of really low cost devices which seemed to want to interface to something through IR, which didn't seem like the right answer.

Does anyone have an inexpensive (<$100, or at least < $200) way (both hardware and software) to control a Talon SRX (in encoder mode) which includes both driving at a specified speed and driving (a single encoder) to a "click count"?