Most desktop PC can have a RS232 card installed which would allow you to continue to connect to a cash drawer using COM1. They cost usually under $20.
Basically the industry just no longer bothers shipping PC's with RS232 or Parallel ports since few of these are required.
About the only challenge might be getting the driver installed if using Windows as these are considered "Legacy Hardware" which you may have to select in the 'Action' section of the Device Manager menu.
You might be able to also use a USB to Serial adapter to connect to the device.
See, not all dinosaurs are extinct.... yet