Save a search on eBay. I've had three 1984 Trek 850s over the years, none that large. Nicely equipped too, so if you find a complete bike, thats even better. The early Trek MTBs were special, numbers were reused over the years and appear on bikes that share nothing in common.
I'd also check FB marketplace. Start with Denver. I've found a lot of nicer vintage MTBs there, including two of my three 850s.
The search function in FB marketplace is horrible. My "trick" when planning a road trip is I do a simple search for bicycle or bike, change the location to larger cities along my route. Its how I scored a nice Diamondback Mean Streak in Des Moines. I was on a road trip to TR National Park. Met the seller at a gas station. I regularly see nice bikes on FB marketplace at attractive prices sit unwanted for several weeks. Sure, stem and bars were a disaster, but the bike itself was in very nice condition overall. Asking price was about 1/3 what the pedals alone were worth.
Fortunately, I am agnostic on size, brand and model, which opens up a lot more deals.
