The only time I could see a military unit or regiment being able to buy "what they want"; would be if it's SF, SSF, SO, etc. Even then, there must be strict rules to adhere to. I would have to imagine that a SEAL team for instance would have nearly whatever they want, supplied for them. Within reason of course. So most likely you'll see small personal gear touches, instead of primary pieces of kit.
Those that buy loads of high end gear from a tactical store would most likely be a collector, or PMC. But there is no direct correlation to me buying out the whole store, and someone doing their job. It's a business, they don't care who's buying their product. If a soldier (private or government) has a job that hinges on the fact that a certain piece of gear will be available at the retail or online level "right now", they're doing it wrong.
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