The external batteries look great but some of them have a slippery surface which is very slippery, and is even worse when it’s in the pouch. As soon as you open the pouch the battery can fly out.
Would anyone else like to see a maybe a rubberised finish?
I find the current PowerCore plastic finish grippy enough. My old Astro3 was very slippy gloss plastic.
If you need it grippy though, buy some tennis/badminton/bicycle handlebar tape. Just wrap it around and “Hey presto” grippy finish. 
You know what would be super cool? A Sandstone finish like OnePlus’ phones and battery pack. The sand like finish is super good looking and grippy.
I like where you are going with this. Have you looked or felt eh PowerCore 5000? It has a rubberized finish that I feel would satisfy your needs.
The rubber might but 5,000 mAh is if no interest to me.
Can’t say that I do; I actually like the smooth anodized aluminum finishes, and matte plastic finishes of Anker products these days. It catches less gunk, easy to get in/out of my pocket or bag, won’t wear ungracefully… yeah. I prefer if those kinds of things were add-ons rather than built-in.
Funny you ask. I immediately thought no, it is fine. But then I remembered I dropped it the first time I held it. so I guess it makes sense.
picked up a Powercore 10000 - doesnt feel slippy.
Picked up a Powercore+ mini - feels a bit slippier but its so small I’d be a dork to drop it.
the plastic on the powercore is perfect. i wouldnt like rubber because then it would stick to the inside of my pocket