Even 20 years ago the public sector was perfectly on-board with so-called "catalog purchases" using approved retailers, and "payment card" (e.g., company credit card) without prior approval. I don't know where your experience may have occurred but purchasing and supplier management process actually helps most places get what they need rather than hindering it.
Some businesses can hand the expense straight on to the customer.
Government 'cost plus' contracts are that for example. If you are contracted to build a bridge, the concernment will pay for all the hours your employees worked on it, and all the concrete and steel they bought for it, and some profit percentage.
In public sector... “telecom expenses must go through telecom”, and they may not be willing to bother with the paperwork.
And god help you if you’re working in some kind of private-public partnership where that $9 expense is -$9 profit.
Sometimes you can get around it if you can find what you need from Staples and order it as an office supply.