For my KX3 + side panels + lexan cover, I rely on a tactical water bottle pouch. I jog with the KX3 in this and beat the heck out of it. Protects the KX3 through my abuse!
This is what I have (Amazon): http://a.co/1HEVT1I
Since the bottom isn’t padded I cut a piece of foam to fit in there. Also, the top is fairly padded, but there is about 3/4" of space above the radio. I fill this space with a round headphone case (see picture below). I actually have 2 of the small headphone cases. One holds my pico paddle and cord. The other holds my earbuds.
There is also an ample side pocket on this case. I put in my 2200maH LiPO, power cable and second headphone case. Makes it really handy to do a gear check with most everything in the same pouch.
I did have one of the bigger KX3 heatsinks on the rig, but it wouldn’t fit in the case with it on. So I went back to the stock heat sink (more than adequate for CW operations). I think if you had one of the lower profile aftermarket heatsinks it would fit in the pouch. With the stock heatsink it is a perfect fit.
Here’s a picture of it while QRV. I can take more pix if you want.
GL es 73 Jim/K7MK