When I commute, I rarely have a pump on the bike because I’m afraid it will eventually get stolen (like my lights a year ago). Having it on the bike and then take it with me every time I park my bike, wouldn’t work either for me, because that would require me to wear a backpack as well. So, I’ve decided a long time ago to have a pump only on the bike that is used for bike trips and live with the possibility of a flat tire in my daily commutes. But, as the experience taught me, this possibility is not negligibly small at all. In various occasions I had to drag my heavy bike for 5 or 10 klm.
Having thought about all that, a small hack struck my mind. Why not strap a cheap pump with a reusable zip tie? That way the pump is safely secured on its mount and makes a possible thief to put some effort in order to figure out how the mount releases the pump. That effort requires time and time is a luxurious necessity for opportunistic thieves. Especially if your pump is not that fancy!
Also, reusable zip ties are not that common and most people don’t even know they exist, especially if you hide the part that makes it recognisable under the water bottle. If they want your 8$ pump, make them work!