I've got a baby boy who is fast approaching the age where he will play properly with Duplo. As it stands we have a mishmash of bricks but what I really want is close to 100 of the standard 2x4 pattern, the real generic "house brick" type block. I had a look on eBay which was passable but not great, and I tried brick owl and either they didn't have them or I was using it wrong. Is there an easy way to get a load of these blocks? Are they a popular thing for sale in AFOL forums?