Rig Rite will probably not help you much to determine what you need. In my experience, they are not friendly over the phone, though they do supply you what you order well.
You will need to measure your mast to determine which mast section you have. You will then determine which mast base you need to get. It will be different than what you have, which was a casting that allowed internal halyards to exit out the base through sheaves. You will need a base plate with hinge. You will need a spacer block to make up difference between plate and the old casting. You will need to cut holes in the sides of the mast to exit the internal halyards. You'll need cover plates over those slot holes. You'll need stand up blocks to bolt into the base plate, so the halyards will turn at the base and cleat up to the existing cleats alongside the mast. If you ever wanted to lead halyards to the cockpit, now would be the time to do that, though I don't think it's necessary on a 192, or that there's much room for hardware to do this on the cabin top.
I'm not sure of my schedule, but I might be able to get a pic of the completed repair from my friend's boat. I think based on this info above, he was able to find the correct parts from Rig Rite's site, because I don't have an email detailing part numbers to him, so I think he looked up everything himself.