small (pea sized) pieces of hot dogs, mild cheese, any cut of beef (also heart or liver) or chicken breast baked until done and chilled overnight (makes it a lot easier to cut), "fish fudge" (pureed canned salmon, mackerel or sardines mixed with enough corn meal and an egg to make a thick batter, then baked on a well oiled cookie sheet until done)...
the possibilities are endless, but of course you'll have to find out what motivates your dog. one treat may be accepted ok but won't do much in a high-distraction environment.