Is there any substitute for vital wheat gluten?
No, there is no substitute for gluten, at all. 

The gluten + soft flour combination is itself a substitute for bread flour, so if you can get bread flour, as Catija suggested, use it. If you can't, you need another recipe. Especially if your goal is to "not make it complicated", don't use substitutes. Substitutes are always complicated. The easy thing is to follow a recipe without making changes, and there are thousands of good recipes, so if you can't make one, choosing a different one is easier than looking for substitutes. 

Seitan is not a substitute for gluten, even if you grind it up. In seitan, the gluten is already set, but you want it "raw" for making dough.