Make sure the motherboard of your next computer really hasn't COM ports. Many mobos have internal plug(s) for COM port(s). It only requires a PCI bracket with a COM port on it with its ordinary cable that needs to be plugged into the mobo socket. Very easy to find in most PC assembling stores.
In case your mobo hasn't any COM socket, USB to COM adapters work fine. There are many on the market. I have several no brands ones. It only takes drivers installation.
If you want to go the "trendy firm" way, you can get a Keyspan one, which is quite expensive (like 3 or 4 times the "no brand_no name" ones…).
Both solutions have proved to work fine and reliably in the years. The Keyspan has drivers for Mac OS too.
Make sure the one you buy has the drivers for the OS version you choose…which I advise to be Win 7 if your choice is a MS pc.
all the best