I've found chicken, lamb and beef make for high value treats.
If you want firmer chicken strips, I suggest baking or even pan frying them. For all of my meat treats I first use a meat mallet to flatten the pieces. I then put them place them on a baking rack over a tray (to catch any drips) into the oven at a high temperature. I bake them for as long as it takes them to get a bit crispy around the edges, 20-30mins. Let them cool for a little bit before cutting them.
But for general training purposes I also buy dried liver and kangaroo pieces which I break up. If there aren't any stores that stock dried bits of liver etc, maybe try some of the local markets. I know they're my favourite source for doggy treats!
But don't feel too bad for treating food that has other additives in it. I truly try to avoid any of these foods, but occasionally I need treats that can last without refrigeration.