non male come idea... non so quanto possa essere pratica per l'uso nel sa (la vedo piu' utile a chi guida mezzi), in pratica e' come avere una piccola nalgene con il tubo:

https://www.tacticaltailor.com/joeyhydrationpouch.aspx





in acu, tan e nero a 45$ vescica da 0.75 inclusa.

the joey pouch is designed to be a smaller alternative to our larger 3 liter hydration systems or as a replacement for a traditional canteen. for use with .75 liter bladders, the pouch features mil-spec construction from 1000 denier cordura nylon with a dual-pull heavy duty zipper and external webbing and will also hold a standard nalgene bottle. attaches to molle/pals style webbing with two included long malice clips®.

the joey pouch is available with or without a source .75 liter kangaroo bladder. the bladder features a quick-release braided drinking hose, high flow valve, a filler cap that doubles as a drinking valve, a glass-like inner liner for pure taste and microbe resistant material to hinder mildew growth. available in acu, tan and black. black pouch not available with bladder.
la vescica "kangaroo" e' venduta anche separatamente:

https://www.tacticaltailor.com/kangaroo75lbladder.aspx

a 23$.