Other critters. Birds, mice, etc. Have any pigeons around? A place to trap some mice, voles, etc? Have also used store bought meat, chicken
There are "lures," never tried them.
I've trapped some in Pa. They are smarter than other critters. I camo'd - disguised - the trap into the area I was trapping in. Make it look like part of a hay bale, etc. They wouldn't enter a free standing trap for me.
Even then, sometimes I would bait the trap, but not set it, to condition the fox to go all the way into the trap.
If you use a Havaheart trap or anything similar, you really have to go all out in making it look natural, like covering the outside AND the inside with brush, grass, etc. But your best bet would be to ask Gobblergetter. He's like the Wayne Gretzky or Michael Jordan of trapping.