Find a picture (in here) of a stock converter. Show the picture to a local shop. My shop said they knew what kind they were -- just by my description. (I gather there aren't many with a triangular shaped "cylindrical" converters -- with ODB2 compliance.)
Interestingly, I'd wonder if/how codes were handled with the original removal? Certainly, you could do universal bullet cats -- if codes weren't an issue...and I'm betting that would cost less.
Finding a place to install a glass pack might not be necessary. You could, instead, install a resonated tip. Getting the tailpipe beyond the rear of the vehicle helps with sound reduction. Of course, there's a fine line between sticking out too far (bust a shin) and not going far enough. The beauty of those clamp-on resonated tips is their adjustability.
I don't think you have a question about the Walker, which means the final question is about installation costs. In general, I would expect to pay about $60/hr for installation. Replacement of converters and the muffler shouldn't take a welder much longer than a couple of hours. But, I don't know if/what remains of the O2 sensor bungs -- or if that's an issue.
If $120 was the price for a single weld-on muffler (sans the muffler itself) you overpaid for that first installation. I had a center converter cut out and replaced with straight pipe (on my Corvette this weekend). It cost me $40. It probably would have been $30 but I took awhile to decide what to do -- in lieu of a converter failure after only 3 months!