The AP2 has been out of production for a long time now but occasionally you can find some on eBay or try a used club retailer like 2ndSwing.com. The current model most like AP2 is T100 but they are quite a bit different in look and performance.

3 and 4 irons are often sold as singles on resellers (used) like e-bay and iron finder type websites. Once someone buys a boxed set and can't hit one or both, they may sell the unused one. Other singles (5-P) are hard to come by.

Titleist only sells current models. The chassis of the 2021/2023 T100 is a different build and feel but is the closest to the AP2.