If you want veggies, leafy greens are your safest bet--spinach, romaine, (iceberg lettuce is worthless), arugula, celery, mustard greens, parsleyetc.
Get Corrinne Netzer's book and then you'll know the fiber and carb counts of everyting under the sun.
I've done a keto diet and found that a small amount of berries or melon didn't knock me out of ketosis, but then, I could go up to 45 grams a day and stay in ketosis.
YMMV