I have the same problem - the safety glasses from walmart sound interesting. I bought these from Amazon and the are good. The magnification is on the top of the lenses where you want it an I am able to focus on the front sight. They are not perfect however, I would like the magnified part to be a bit larger but they do work and are more comfortable than readers I have tried.
https://www.amazon.com/SSP-Eyewear-...hooting+glasses&qid=1554249063&s=music&sr=8-6
https://www.amazon.com/SSP-Eyewear-...hooting+glasses&qid=1554249063&s=music&sr=8-6