You've gotten reference to two sources above. Regardless, you'll want to do your own screening and I'll suggest still keeping ability to you and partners to ride separately if necessary.

I do much of my touring alone, but prior to cycling from Amsterdam to Vladivostok, I placed a "companions-wanted" ad in Adventure Cycling. My motivation was in part because I would be in a country for five months where Russian was primary language and I only knew a bit and was hardly fluent.

I had ~20 responses to the ad. I replied to each and also pointed to a web site that gave some further info on my plans and links to others who had done similar rides across Russia. After that I ended up with ~5 interested. All but one dropped off for various reasons (some my choice, some theirs) but ended up cycling with one other person. We lost track of each other once leaving Kazan and ended up cycling separately for 10 days before reconnecting in Yekaterinburg.