P89cajun,
One more option that you have is to get the barrel back bored but leave a portion of the barrel at the muzzle at its current dimension. Back boring increases the diameter of the barrel and doing so will create some choke. However, just as Lee Lapin stated, your costs may run you equal to or more than a new barrel with this option.
A second option would be to just polish the bore of your shotgun with a barrel hone and have the forcing cone lengthened. Many times there is a vast improvement to your patterns by having FC lengthened and the barrel honed. However, just like the previous option, this kind of work will cost you but not nearly as much as back boring.
A good gunsmith can easily handle either of these two jobs.
Finally, the best advice from a previous post so far has been from bowfin which is to get it patterned. How do you know you need more choke unless you have thoroughly tested it with various loads in its current condition. Besides, the fact remains that even after you get the barrel modified you will still need to test pattern the gun. That is the best part of this process anyway, testing!