You could buy it already made or buy some sour cream and add an envelope of Lipton Onion Soup Mix and make it that way.
Well, guess what? Dairy sour cream is bad, bad, bad and that soup mix is nothing but gross chemicals. including MSG.. no thanks!
Onion Chip Dip
1 cup diced onion (I recommend a sweet onion)
2 tbsp olive oil
1/2 cup silken tofu
1/2 cup Vegenaise (or other vegan mayo)
2 tsp nutritional yeast
3/4 tsp garlic granules
1/2 tsp onion granules/powder
1/2 tsp No Beef bouillon
1/4 tsp salt
pinch citric acid (or a little lemon juice you want it a little tangy)
Saute the onions in the olive oil over a low to medium heat. You want them lightly carmelized, mostly brown, not burnt.
Place the rest of the ingredients into a food processor along with half the onions* and puree until smooth. Fold in the other half of the onions and chill for an hour.
* if you want a completely smooth dip, add all the onions at once to the food processor.