Pea's are good, you can also try spinache, tomato and cooked bracalli too . Most fish seem to prefer peas and cucumber on the whole though- its best not to feed fish fruits in general though as they generally contain a high citric acid or sugar content which can give some fish digestive problems.
I wouldnt feed any fruits, but most green vegetables will work fine. To supply greens in my mollies and platy's diets, I feed lettuce via vegie-clip, spirulina flakes, and "Seaweed Salad" which is dried seaweed.
Just about any LFS should stock it, its usually in with the saltwater foods, though its more than ideal for freshwater fish. I use San Fransico Bay "Seaweed Salad" and Ocean Nutrition "Marine Seaweed Selects". If you use Ocean nutrition, only use the Green seaweed, not the red or brown.
Dried Seaweed makes an excellent staple for many livebearers espically mollies, where their large need for greens is usually overlooked by many owners. Dried Seaweed is high in protein and fiber. There is also the frozen variety, which obviously has a much higher moisture content.