If you plan to use the Federal HW 7s(The most lethal 20ga factory turkey load on the market period), a good cheap option is the Remington Extended Super Full. It's a non-ported, extended, .572 choke and does quite well with the HW 7s as well as others. Walmart online sells the choke for $23.
I've rolled many heads with that combo and it flat pulverizes them.
This one. Find the Rem chokes and don't look back. Spend the money you save on more shells...