I use two types of bags , first one is back up when i go for long walks in search for new places to hunt, 30L Rambo model by Nikko , it is more long then wide so i don't separate coil from stern when i packed it, and i use big coil most of time. So measure ur deus packed and u u will get picture how big backup u need, just few pockets will be enough since need to be light.
If i go directly with the car to hunting place then i use old tennis bag, they r cheap and suited it very well. Hope it helps.