If you Google "bulk hockey pucks" then you will find quite a few options that range from Amazon to Howie's. The best price I'm seeing is this 100 puck box on Amazon for $109. So just over a buck a puck.

If you dig a bit deeper, you could possibly find a bit better of a deal on eBay. I remember last year finding a 50 puck box for like $35. That was something like Patriot Puck or similar.