You could probably go even lighter by removing the power/control box entirely from each panel, and replacing it with an after-market board and a common supply f

You could probably go even lighter by removing the power/control box entirely from each panel, and replacing it with an after-market board and a common supply for everything. It's easy to find control boards with HDMI inputs for your LCD panels on eBay, simply search for "<panel reference> control board". The control boards alone are very light, and low-voltage so safe. Presumably your panels are LED-backlit so safe, low-voltage too. You can then use a single external power supply to power the whole thing, easy to find on ebay/aliexpress too. It would also avoid the safety issue of stitching together the 3 power cables, and reduce the weight of cables as well. Then package everything in a nice box with hinges and some padding and you have a nice multimonitor transportable PC ;)