Even though the Industar-69 uses a 39mm screw mount, it was actually designed for the half-frame Chaika camera. That will cause a few issues for you - firstly, if the lens mounts, it will likely not focus to infinity without modifying the mount. Second, because it's a half-frame lens, it will not cover a full 35mm frame. And to top it all off, it is not rangefinder-coupled.
The cheapest LTM 28mm I can think of is the FSU Orion-15, which is a 28mm F6. It uses a Leica compatible-ish mount and covers full frame. You can often find them for under $200. Another good option, though not a 28, is the 35mm F2.8 Jupiter-12, which you could use with your Canon 7's built in viewfinder. These tend to go for $100 or less.