There are no modern printers that do printing over COM port, even most older printers use SPP or EPP parallel (Centronics) ports. The only COM printers I recall were of "terminal" types, with daisy-type heads, or IBM typewriters, 40-some years ago. Maybe some POS thermal receipt printers still use this interface though.
So, if you say it "prints on a COM port", it means likely a very simple ASCII character stream, strings/lines terminated with CR-LF characters. While all USB-based bitmap printers use some high-level language (PCL or PostScript) to control the printer. Even if you map your output to virtual COM/USB port, the resulting data stream will be the ASCII-CR-LF, and no USB printers can understand this.
What you likely can do is to hook-up your COM output somehow virtually to a Windows "terminal" application, and then use the generated bitmap as an image to print (including printers with USB interface). This looks ugly, but the COM-port printing is a blast from deep past.