Depending on whether you just want to buy another choke tube, or one dedicated to turkeys, I'd suggest you pattern the modified tube that comes with the barrel prior to buying another. You may find, with the load you want to use, that the modified choke will work just fine. Just cause it says "modified" or "full" on the tube does not mean it will throw those patterns with the specific load you want to use. Many shells on the market these days, especially the hard non-toxics, throw much tighter patterns than expected with more open tubes.
I really like Briley choke tubes. If the modified tube doesn't get you what you want, try a full or maybe an extra full. I'm not sure that the specialty turkey tubes are worth the price-- sometimes upwards of $75-$80. Brileys are well made and for the flush or plain extended tube, are much cheaper. IME, the standard Remington tubes are also pretty good, especially for the money.
Before people got decked out like NASCAR drivers to go turkey hunting, tons of people used standard full and modified choke guns to kill turkeys.
Good luck.
