[spewing]

in the UK i buy them on eBay

https://www.ebay.co.uk/itm/5-16-8mm-Catapult-Slingshot-Ammo-Steel-Ball-Bearings-Pack-of-2000/371354605575?hash=item5676759807:g:75gAAOSwPhdU2HqW

I don't know about shipping outside the UK but it may not be as expensive as you think (at least while were still in the EU :banghead: )