Buy way more than you need. The shipping is brutally slow from China lately. Over a month wait. But then again they do only cost like 10 bucks per bag. I regret only ordering one bag.
Just search for "pcb feet". You Wil get many options for different quantities.
Seconding what yangman said. I bought 50 about 6 months ago. Thought it would be a lifetime supply. Just used the last of them yesterday and cam up one short. Must've dropped one at some point and thought it wouldn't ever matter. :/