Can you not get one of the special backpacks for enteral feeding, through the company you got your pump from? I'm not sure what kind of pump you have, but I know there are mini backpacks for both the Kangaroo Joey and the Infinity pumps. We got one for Peanut, which is pink and it works awesome. It was made for her feeding pump, so there is a special spot for the pump, one to clip her feeding bag on to, a front pouch that opens so you can adjust the pump and not have to open the whole bag, its nice a small with padded shoulders and back too. There is a special hole on the bottom for the tubing to go through, and a double zipper if you'd rather use that. There is even a chest clip (mind you we don't use that much because it pushed on her port and hurts her). It looks like a normal backpack, which is nice because I didn't want something that looked medical. It wasn't cheap (I think it was 120$

), but it was worth the investment.
This is the one we have, but ours pink.