I bought a little Vivitar V3800N at a yard sale a while back for $5 mostly because the little battery cover was missing (and the owner wasn't even sure film could still be developed.) This is not exactly a camera that gets a lot of praise but it works just fine. 4 years later the cover is still missing and the camera is still going strong. I am sure it is psychological but I can go through roll after roll in this camera without getting all sweaty about it. I don't talk about it much but every year it is one of my most used cameras.
Great pictures as well. :)
Maybe your Yashica Mat will turn out the same for you. Sometimes knowing that the camera is not perfect allows you to look at it a little different then one where everything works. Shove a cotton ball where the battery goes, tape over it with a piece of gaffers tape and go shoot film.