McMaster Carr has box quantities, broken boxes cost a little extra.. if you're local, $20 min order order I recall.. in Santa Fe Springs store, 'bout 20 miles from me, they have a phone on the wall for walk-is orders.. goes to order desk lol.. great place with awesome selection.. been using them 30 years every place I've worked including .mil and my personal use..
Hillco is an awesome automotive specialty hardware store, also local, 'bout 3 miles from me..
http://www.hillcofasteners.com
Mcfadden Dale in Anaheim and Santa Ana always had great selection and early house for trades guys..
https://mcfadden-dale.doitbest.com
good luck!