Thanks for the interesting information, reh321.
I had a look on Pentax CCTV product catalog.
Security Lens | Industrial Products | Ricoh
You can find there a 3-8mm f/1.0 lens, but it covers only a 1/3 inch diagonal sensor. The sensor of the Pentax Q is bigger (1/2.3) and Q7 has an even bigger one (1/1.7). So it means the lens will not cover the sensor (vignetting). Additionally, carefully check the lens is not a CS mount, because the registration distance is much shorter for CS than for C mount, and commercial adapters are only for C.
C mount - Wikipedia, the free encyclopedia
Overall, it would deeply surprise me if you coul find a bright 3mm capable to cover the Q7 sensor. My recommendation could be the Pentax 4.8mm f/1.8, which is good and with fix focus. But the 08 is a cute autofocus ultra-wide lens with few equivalents. After intensive research, I finally bought one because I could not find any equivalent in industrial vision lenses. A cheaper solution can be to buy it new on Amazon.jp and import it with Buynippon.com. But the 08 is an expensive (and excellent) lens. Good luck for your quest.