The Icom IC-R3 and IC-R20 can use either a custom fitted Li-Ion battery pack from Icom, or 3 standard AA batteries.  However, if you use AA batteries, there is special insert that goes into the battery compartment.   When I lost the insert for my R3, I developed this 3d-printed replacement.   It works fine in my R3 and I have received feedback from dozens of R3 and R20 users and that it works for them.   

It's guaranteed to work in your radio, or your money back.

Free USPS shipping to US destinations.   Will ship internationally using the eBay global shipping program, but buyer must pay all shipping costs. 

(Condition:  ebay required me to select New, Open Box, Used, or PNW.   None of those really apply to a fabricated object, but "New" seemed like the best choice to me)