They do show up from time to time. For a first year production gun however you will need to find one serial numbered below 2200 or so. Ruger started shipping their "Ruger Pistol" (later known as the "Standard" model...not a Mark I) on October 6, 1949 so there were less than a 3-month production run for 1949. To add to that, there were no guns serial numbered from 0661 through 1999, so that leaves around 860 guns for the production year.
That said, Ruger's first production model with a red eagle medallion in the grip is a surprising "sleeper" among collectors as you can usually find any of the 11 "Standard" model variations with fixed rear sight in decent collectible condition for $600 or less, with patience of course.
For a true Type 1 Red Eagle you will want to be sure the bolt is original (in the white and without a recoil spring support) and the grips will have silver colored escutcheons around the grip screws.
At one time there were maybe a dozen Red Eagle collectors who endeavored to find each of the major variations, including the Mark I with adjustable sights. But since those collectors have long ago filled out their collections with these scarce guns, there aren't many folks looking to build a set, which gives the original red eagle auto series serious investment potential.
Chet15