We just bought them on Amazon so I don't know about where else you can get them cheaper in bulk. But they've been an absolute favorite of my kids for 5+ years. Especially for travel - we often take a Ziploc size amount and they do it in the airport, at the hotel, basically any downtime we need to fill it's a creative engaging way to pass time.
For what I'm describing above - they are a lot smaller and lighter and Legos.