This is not really a forum for doing business nor is centered around the bulk of it's members owning a lot of the gear they use.
There are lots of internet sites you might get more hits off of and posting your question on a once a year basis is ok.
Stagecraft, Lighting Network will let you post once a year such a question, and Pro Sound - Lighting board has it's own commerce section. There are a few other company owned forum sites such as American DJ and some gear retailers that have forums for this also.
After that there is E-Bay, lightbroker.com, lightmonger.com, usedlights.com, usedintelligentlighting.com amongst a short list of websites to post or search into. You can also place an add in PLSN or Theater Crafts, much less any arts magazine or newspaper even Equity and might get a lot of hits. Another option would be to contact NSI to see if they have any factory referbished light boards or to look for a list of service centers and tell them to keep an eye out for the light board of your choice so you might make an offer to the owner.
I've seen them every so often on eBay. Thing is they don't have a theatrical lighting section as such - you've got to dig because it's buried under Musical Instruments/Pro Audio/D.J. Gear/Lighting Equipment/Controllers.