This mounting concept can be utilized to secure and stabilize many different items to the BikePackersFoundry handlebar strap system. It’s a simple as sewing a length of correctly oriented Velcro OneWrap to the bag that you want to attach. Ten centimetres (~4.5″) should yield enough engagement to have a secure overlap with matching strap. If the bag lacks a location to loop through the strap you can add a loop of your choosing.
A length of onewrap has been sewn to the back of the pouches. 
Bear spray & wildlife horn mounted 
Close up of wildlife horn mounting