I came across this Trane refrigerant monitor, it came out of a building being remodeled. It's practically brand new. I don't know much about the value of these but I've been looking around and it seems they are pretty expensive. Here's some info on it:

RMWG Refrigerant Monitor

This RMWG refrigerant monitor can be configured as an either self-contained unit or a split system (control module and a remote mounted sensor). Both configuration types can have additional sensing points added later on. This allows a system to grow whenever new ports or new refrigerants are required.

20 ppm sensitivity – meets ASHRAE std. 15 and most local building codes
UL certification for fire and shock – provides third party certification
Diffusion sensors (single channel sensors only) – provide high level of trouble free operation due to lack of moving parts
Pumped sensors (four channel sensors only) – provide quick response to increased levels of refrigerants
Max up to 8 sensing channels – gives user a choice to expand sensing points in the future
Up to 5 different refrigerant types (R11, R12, R22, R-123, R-134a) sensed at the same time – provides flexibility needed to meet the needs of the most demanding applications
4-20 mA and 0-10 vdc standard output – sends input to any building automation system
4 relays (3 levels of alarm and fault indication) – activates alarms and building ventilating system in response to alarm signal
85 dB buzzer (optional 110 dB buzzer) – standard buzzer (optional unit mounted beacon, and warning lights are available)

I'm actually not in HVAC, I'm a carpenter. I don't know too much about this item, so please let me know what you think and make me an offer.

I have it listed here:

there are pictures available on that site, and I can email more to anyone interested. If no one is interested, please point me in the right direction of who might like to buy it.