Cloudynights forums have a target of the month in one of the subs, and I'd also try opening/looking for an existing thread on astrobin forums then organising with like minded individuals.
If you join Astrobiscuit's discord channel his whole community is essentially centred around group collab efforts - check out this vid where he announces the BAT - Big Amateur Telescope:
https://www.youtube.com/watch?v=4rCyC3_YIME go to 27:52.