In most Units, private purchase plate carriers / chestrigs etc are still forbidden. Some of the more enlightened RSM's out there are starting to let private purchases of these items into use, based upon various interpretations of "approved use" lists floating around out there, but these are still far and few in between.
The vast majority of CF pers requiring load bearing gear are using the CF issue TacVest, despite it's severe limitations and supply shortages of them in the system. Hopefully when the new SORD chestrig/LBV/carrier package comes online for use in Combat Arms Units that will mean more TV's for everyone else.
I call bullshit on the commenter, and would put forward that supply shortages from 3rd party manufacturers of military gear are usually due to massive orders from government orders than from random individual civilian orders. For instance, the reason why OPS CORE helmets are impossible to get right now is that a particular US SF organization submitted a massive order for helmets last November, and OPS CORE has been busy pumping that out on their production line ever since.
Order what you want, don't worry about depriving someone else of gear; the failure of a gear manufacturer to plan their production line accordingly is not your problem.