I use the HPG small pouch. I don't have the new First Responder Kit bag, I have the Heavy Recon Kit bag that I use for SAR. I also have the original Kit Bag I use for fishing only.
The small pouch works well with my radio, a Kenwood TK 2170. The 2170 measures about the same as your radio except yours is about 1/2 inch taller. My 2170 measures 4 1/2" X 2 1/4" X 1 1/2". (Tall wide depth).
Hope this helps, Have a nice Holiday