I had a cat efficiency code on my Insight, and eventually ended up buying an aftermarket cat… it seems like you can get the rear catalyst from Honda, but the front is only in a front/rear kit (at about $1k). This is a 2000 so it doesn't monitor the second cat.
The two prices were for different years: parts 18160-PHM-A00 vs 18160-PHM-A20. There's a third O2 sensor port on the later part, but maybe other hidden changes. My link only shows one year but your link shows both under diagram #5.
NOx absorber catalysts are pretty unusual, but they're basically the same as a normal catalyst. I think even the scrap value is more than $40. Although the parts place did label it "converter" the too-good-to-be-true rule of thumb applies here.
