They are out there, but they don't come cheap. Over the last 6 months I bought both a 6.5" and 5" version. Both are no dash models, and both came through private party purchases. I wanted them for use in the local Icore matches. I originally started out thinking about a model 625, but when I found out about the capabilities of the 10mm, I decided that a 610 could do double duty for close range deer hunting and competition. On the first gun, I went through all the back and forth e-mails working out the deal for the 6.5" model, all the while telling my son about the deal I was working on. Well as it turns out he talked me into letting him buy the gun for Icore since I already had a model 627 that I was using. So I caved. After seeing how well his 610 shoots, I knew I had to find another one, so I posted some wanted to buy ads here and on a few other forums. I really expected my search to take several weeks, but as luck would have it, someone needed money to fund another gun, and saw my WTB ad. Since he had one stashed in the safe that wasn't being used, and would give him quick access to the cash he needed for his new project, he contacted me the day after I posted the ad.
Like I said, they are out there but they don't come cheap. I'd call paying $800 a good deal, up to $900 a fair deal, and between $900 and $1000 an average deal depending on condition. I have no problem buying a gun with the lock, especially if it will be used for competition, as opposed to being carried for protection. My 627 has the lock, and I have never had any issues with it. Of course if I'm buying a gun with the lock, I expect to pay less than a no lock version. To my way of thinking, the only drawback on models with the lock is the reduced number of people interested in your gun when it comes time to sell, so I expect to pay less when I'm buying.