Yes, 001-646-940-00 is the OTG adapter cable for the XL units offering that feature.
If you are not worried about water protection at the back of the display, a standard HDMI cable can be used directly to the unit at the back.
The BBX has standard USB and HDMI out (and in) that unless you wish to get the water protection adaptors, you can just an external monitor right into them. The OTG connection is when trying to bring HDMI in from something else like a laptop where you want touch control.