As far as i know no other brands have OS/2 drivers
That is indeed (mostly) correct. Minor wording change for accuracy.
Many serial connected touchscreens are OS/2 compatible, but only those
manufactured for the re-brander by Elo or MicroTouch.
That includes a variety of Sony, IBM and other CRT or LCD touchscreens for instance. As a matter of fact, at one point, the majority of touchscreen CRT and LCD units had an Elo or MicroTouch touch panel inside of them. The problem is determining which contains such a unit and how the touchpanel interfaces with the computer.