I have what I believe is an old king arms ACOG non magnifying red dot, it's broken the brightness switch broke off so now it just good for looks-$10
I also have 16 size (13) hearing aid batteries that worked in the ACOG before it broke-$10 They might work with other red/green dots or holo sights, here's what the size (13) is also called by other brands- DA13, 13HPX, AC13E, AC13, 13A, 13AE, R13AE, PR48, and L754. They are duracell's
Here is a pic of the ACOG