I used flat shim washers but often you need more than your supply. Thus, I decided to find a reproduction equivalent that reduces the number of shims required. One of these makes up the same as several thin versions

This item fits the 1/4" square (.28" actually) and can be reverse stacked to close the distance or just nest.

Solid in lots of six (6).. Free shipping.

See my other listing numbers below for more "Hard-to-find" lock parts