Could just lift the needle, lift the pressor foot, and move the fabric forward a tiny bit such that the needle steps back one stitch length, lower the pressor foot and the needle again, and then continue sewing forward.
This would be quick to do and accomplish the lock stitch you need.
I do this on an older machine that I like to sew with, and which has a reverse lever alright, but which lever is clumsy to operate. I call it "back step stitching" and it works fine.
.