One suggestion..............order them on-line from Mouser or Digi-key. Ok, you would have to buy a bag of 100, and pay shipping. But on the plus side, you could have them waiting there for you.
Expect to pay a quarter apiece for stand-offs.
An alternative......although somewhat hit-or-miss........hardwares stores sometimes have stand-offs in those plastic pull-out trays in the hardware section. At least here they do. The trick is to find a hardware store these days.
Good luck.
Pat