Some of the best chocolate in the US can be found at See's candies. I happened to know someone who once worked at the chocolate company that supplies chocolate to Sees: it is the Guittard chocolate company. The don't sell direct so you can't buy their chocolate by itself, though looking at their website I think you can buy it direct from them.
I mention this in case anyone wants to try this 3D printer idea out. Engineering projects should use the highest quality materials! I'll happily volunteer to test your final product.
antedeluvian I live in the US. I'm a big fan of Cadbury's Dariy Milk. (Hopefully, the recipe will not be "improved.") And, I got my children hooked on Aero bars when we visited the Canadian Rockies last summer. I'll look for the things you've suggested. :-) I'm also a long-time fan of McVite's Milk Chocolate Homewheat biscuits from the UK. American chocolate, for the most part, tastes like wax to me. A nice belgian raspberry truffle would be kind of nice right now...
The same brand of chocolate is made to different recipes around the world. Cadbury in Canada is different to Cadbury in the England. (Who knows what will happen now that Kraft owns Cadbury?) Often we are conditioned by the taste we are used to, but if you want a great taste experience you should try and get hold of Cadbury's Top Deck from South Africa (it is a milk chocolate base with a white chocolate upper layer)- I don't know where you live, but there are sources of South African products around North America.
Also the greatest "cookie" (biscuit) is the Tim Tam from Arnotts in Australia. You can certainly find it in supermarkets here in Canada. It is a chocolate covered wafer. They tell me (I don't drink coffee) that the very best way is to bite off both ends and drink your coffee through it as if it were a straw.
When it comes to chocolate, as far as I am concerned the shape is irrelevant. In fact the passage from bulk to my mouth may bypass the extruding process altogether. However here's a thought- it could be used to change the texture to something like Aero. I could be interested in that.