Here are some items you can use when you want to grill outdoors (and indoors).
The Grill Grate Sear’NSizzle for Ninja Foodi Deluxe 8-3/4″ Diameter Grate will fit the 5 quarts, 6.5 quarts, and 8 quart Ninja Foodi the 8 quarts Instant Pot Duo Crisp + Air Fryer. When looking, this thing seems legit. People use it to get real grill marks on their food. Many of the reviews I watched on YouTube show very juicy and promising results. So while I have not used this product yet, I feel very comfortable recommending it.