I *think* I may have answered my own question using this Standardized Headset Identification System document linked on the Problem Solvers page:

http://problemsolversbike.com/files/..._standards.pdf

It appears that this bike has a standard 1-14 (EC37) headtube bore, meaning the bore of the headtube where the cups get inserted is 37mm (1.456"). I measured 1.45" so close enough. The only other concern is the insertion depth, but cycle_maven already did it without issue so it should work for me as well.

Thanks for your help! Looks like Problem Solvers part number HD9900 is what I need.