I feel your pain
Was going down to Mom G's today to do some yard work and needed my trusty Echo trimmer. In changing from the brush blade to the string trimmer, one of the guard screws broke. Luckily some of it was left sticking out the other end and I got it out with some vise grips.
Dropped by the hardware store on the way down and had trouble finding the metric section. (no, I won't ask for help). Tiny 5m x 30 stainless replacement screw, $2.15. Went with the bright zinc instead. After I found the metric section.......