Kale, collard green, escarole, endive, radicchio, romaine, and other varied greens. Also I buy grass & weed seed from sulcata food.com and plant it in my leopards outdoor enclosures. Sulcata's & Leopards eat the same diet, leopards just eat less.
Most leopards won't eat dry hay. Some of them will nibble grass, but unless you have the pp subspecies thats not a large part of their diet.
You need broadleaf weeds, leaves and various succulents. Red apple, ice plant, elephant bush, jade plant, spineless opuntia cactus, etc. There is a weed ID section over in the diet forum here. Check that out and see if any look familiar. Just make sure you get them from a chemical free source. You can also grow your own grape leaves, mulberry leaves, hibiscus or rose of sharon leaves, or gazania, pansies, nasturtiums, roses, etc. If you can't do any of that then you'll have to use grocery store foods like endive, escarole, cilantro, carrot tops, collard greens, etc.