1x4 Duplo Bricks?

natsguitar

In my childhood Duplo collection (which my son plays with now) I have a handful of 1x4 Duplo bricks, and a handful of 1x4 Duplo plates. I can't find more of these bricks/plates anywhere, which makes me suspect they are not actually Duplo, but some other brand.

Has anyone seen these pieces? Where could I get more?

Calibrick

Could you possible post a picture of one so we have an idea of what you are talking about? That would be a big help, thank you! :-)

Hoddie

Possibly Lego Primo?