That's annoying isn't it. I use a Fletcher Tru Peep. It uses no tubes or anything. With just a little tinkering and a string that's not stretching, you can get it to stay pointing in the right direction.

A string loop tied tightly will often perform just like your Ultra-Nock did. It will, within reason, prevent the string from twisting too much as you draw. In fact, on my last bowstring, my loop was tied on so that it stuck out on the right hand side of the bow. When I drew the bow, the loop would rotate the peep into position just like an Ultra-Nock.