Depending on how handy you are with electronics and code, you could pretty easily build your own. I have an Arduino currently running a small column mounted display and have gotten fairly familiar with how the MS CAN works. I have debated using some of the extra inputs on it (or buying a whole separate one) to get extra inputs into my MS. The biggest idea I've had for a while now but haven't gone through on is building a dedicated "sensor unit" that I could mount in the engine bay and wire all the sensors to. Then I would just have the CAN lines to pass through the firewall instead of all the individual sensor wires. I still have a ton coming back out to run sequential injection and the coils, but it could reduce my pin counts quite a bit. Right now I have one ~20 something pin bulkhead that is just sensors and a second one for the injectors and coils. The MS is a little limited on CAN channels though, and I'm not sure if it would play super nice with that idea or not.
But an Arduino Nano and a CAN bridge of some variety would likely only run you $20-25 and would give you something like 5 analog inputs, 10 digital inputs, and the option to use some of those as outputs instead if you wanted. I'm currently emulating part of the JB Perf board to send GPS and RTC data from my Raspberry Pi back to the MS for logging.