I don’t think they are very common. My first surefire was a gunmetal 6P with press-fit lens. it was stolen from me in the early 00s and I got the urge to replace it around a year ago. When I was looking, there was a newer production 6P-GM perpetually appearing on eBay for nearly $300 but I managed to find a similar one for $140 after about 6 months. It’s not exactly the same as the one I had back then. I have not stumbled across a press fit 6P-GM for sale since 2003.