Mine are 4” long by 1.75” wide by 5/8” high. I bought them here: http://www.bakedeco.com/detail.asp?id=329&keyword=barquette
Not sure about the non-stick question. I generally shy away from darker pans as my oven runs hot, plus I have enjoyed using other pans with the same finish with no problems (savarin ring, madeline pan).
The Gateau Breton didn’t stick in the barquettes at all, and for those I just brushed them with clarified butter. For the biscuit, I sprayed them with Baker’s Joy, and they did stick some even after running a knife along the sides, but it was just a matter of thin patches of crust, it wasn’t larger chunks of cake that were missing, so it was no problem (I did not line them with parchment). For the nougatine, I did take care to loosen the nougatine from its mold while still hot, then let it cool in the mold just until hard enough to hold its shape before removing it.
A non-stick finish would probably be better, but I seem to do OK with the regular ones. If you thought you might want to use them in a presentation with the bottom of the barquette facing up, or with less buttery sponge-type cakes, it would probably be worth it to get the non-stick.
Let me know if you decide to make them and you’d like additional notes on the nougatine shaping.