I started to make a set for my M40A1, but never finished because I didn't want to have to remove the scope to finish the project. But, here's what I did.
The rear is easy. You should be able to find a peep sight that fits the rear bridge screw holes.
For the front sight, I did not want to alter my barrel (ruining the M40A1 "look"). So, I got a 1" Redfield rear scope ring, and had a machinist mill a dovetail across the flat bottom of the bottom ring (the flat that sits on the base). This is to mount a standard dovetail front sight (height to be determined). I slid the ring (up-side-down/sight up) up my barrel until it found its 1" diameter barrel position, marked the barrel with a pencil. Then I took the rings apart and reassembled them on the barrel just slightly behind the pencil mark so the rings were tight on the barrel and the sight was vertical. Then I took a center punch and lightly put reference dimples in two spots where the ring/barrel juncture near the top. The dimples on the top of the barrel are barely noticeable unless you know they are there.
Once sighted in and removed, the zero should be pretty close once reinstalled- close enough to check with just a few rounds.