Used to work in a warehouse in my mid 20's. If I could go back I would use my Squarehead. Doesn't have a decent handle like you want, but it works ok with gloved hands. Hang it off a lanyard on my wrist or a retractable keychain on my belt. I used to open boxes, set my knife down, grab product and walk off forgetting my knife. Retractable keychain + Squarehead is perfect combo for this. Small and cheap enough so you could carry 2 in case one gets gummed up from opening boxes.
Maybe not the best for cutting down boxes or those poly straps, but maybe something like a Squarehead/Tenacious combo would have you covered.