This runs on 2- cr2032 disposable batteries.
crimsontrace.com/products/laser-sights/laserguard/lg-489-laserguard-for-smith-wesson-mp-shield-and-mp-shield-m2.0-940/01-3560.html

Josiah, this takes one 1/3N 3V lithium or two 357 silver oxide batteries, which batteries typically provide four (4) hours for the red laser. Have a great day!

easy to replace batteries

Josiah, you have to replace the batteries Sir. It uses (2) #357 Silver Oxide Batteries for (4) Hours of constant on Laser life. This chart shows the alternative compatible batteries to the #357 : -- batteryequivalents.com/ag13-sg13-lr1154-sr44-303-357-a76-lr44-battery-equivalents.html