Bob,
Check the thread specs where the chuck would mount. It should be in the owners manual if you do not have one check Grizzlys site.
Once you know go to
www.pennstateind.com and see if they have what you need. I'm assuming you are going to put a round router bit in it?
Nova chucks are also out there but so is their pri$e.
I have had good luck with PSI & they have great customer service.
Let us know how you make out.
Chris