On the low side the SSX by Truglo, next Carlson's, then Trulock,.
The choke made by Sum Toy will be a little more expensive but do a great job for you.
That is one of my best shooting pattern guns but 40yds is my limit and 30 is my longest desired shot for any gauge.
Federal #7 then Hevi - shot #6 or #7 in HTL
Federal FC #6 copper plated lead or Win Supreme #5 in lead . I also like the older 3" Win Supreme #6 shot that were only available in boxes of 25. Get em close and know your pattern and any of these will do what you want , chokes or shot choices.
If you haven't shot a 20 before the patterns do not look like 3 1/2 " mag #6s in any load. Good luck and be safe.