Don't know that you'll have much luck fitting in a Datrex water pack without tossing other essentials. The water pouch will take up quite a bit of room in that little M-1.


How about upgrading the already-carried plastic sandwich bag containing your first aid items, to something a little more heavy-duty, with modestly more bulk, e.g. Gerber bag, Ziploc quart-size freezer bag, Ziploc Zip 'n Steam. The plastic bags provided in the produce or meat departments of the supermarket are fairly large, strong, water-tight – when rolled/folded, take next to no space. Hold water well if you loosely knot the top after filling.

Maybe this is cheating on your requirement not to increase pouch-size, but have you considered carrying the Leatherman on your belt in a separate pouch? Something like the TAD S2. Would free-up some space; probably wouldn't notice if next to your already-worn cell phone holster; you wear a jacket, so would cover-up nicely (assuming doesn't violate concealed weapon laws).

The M-1 is cool gear, but you're losing interior storage space to the design/construction of the M-1. The 1000-Denier material, divided compartments, and front flap (with cramped zippered-storage) and quick release snap are great, but all that takes up room. How about a similar-size pouch, but a little simpler in design and construction, e.g. lighter fabric, one large compartment, etc.