"Home care" type stores are a good place to get them, they don't even have them behind a pharmacist counter, you just find the aisle, grab as many needles and syringes in whichever sizes you need and carry them to the register to pay. The kind of stores that sell medical supplies like crutches, knee bands, heating pads, etc etc
Even a local protein/supplement store near me has needles, alcohol swabs etc in an aisle next to tubs of protein.
I'm surprised some people can find gear easier than needles.