A cheaper option would be to just cut it down to 18.5-19" which would give you cylinder bore and the very "handi" length for taking down and stuffing in your backpack, I have done this very thing but used a 20 gauge vs. the 12 gauge. Then experiment with different types of ammunition to get the pattern you want. For example a soft lead shot load through a fully cut wad will give you a very open excellent close range pattern for taking game in close lets say under 20 yards when fired through a cylinder bore. While an uncut wad and hard steel/heavy shot/tungston shot will still give you tighter than full choke pattern performance compared to the soft lead shot example above--my experience in the field and at the pattern board which I will be doing more of tomorrow in preperation for this years upcoming waterfowl season is that the type of shot and the type of wad have alot more to do with pattern density/size than choke tubes do. My experience has shown tight chokes don't pattern any better than cylinder choke guns when you find the right wad/shot combination inside of 40yards for the distance you plan to shot at. I have had amazing performance with black cloud steel loads and wingmaster HD loads at 40 yards on the pattern board through nothing more than a cylinder bore 20 gauge.
Regarding the poly-choke, they are not bad I have had guns over the years equiped with them but I think you will find carrying 4-5 different types of shot shells will do alot more for you range and pattern wise than the poly-choke will.
Good luck with your project
