Connecting a serial modem to a RPI4

I need to connect an RPI-4 to a serial modem (a Multitech MT1932ZDXK, to be exact). I recently purchased a pretty blue USB to UART serial console cable from Pimoroni, which I thought might do the job, but it doesn’t. It allows me to connect various GPIO pins to a USB connector that I could plug into my desktop PC. Ideally, I would like a device/cable that I can plug one end into one of the RPI USB ports and a dB25 male connector to plug into a serial device at the other end.

Does Pimoroni sell such a device? I only need it to support 9600 bits/sec. I’m building an exhibit for a local museum to show what we used 30 years or so ago to communicate to a remote computer. The exhibit needs to demonstrate how slow everything was and let everyone hear that magic sound as the modems connected.

You should be able to source an USB to DB25-serial cable from various sources. I don’t think Pimoroni has one.