Try him on some ziwipeak at home. If he really likes it, it's great as a bait, small and easy to carry.
Also, don't forget that some dogs are not food motivated. I used to bait Piper with a toy. She liked the rabbit fur covered mice you can get at dog shows. She'd go nuts for one.
It also kept her happy and interested. She only got to play with it when we were at a show.