Lowes has a 10 pack of Weber pans 2" high . I think they are $9.99. If you are using the entire grill surface you may need 2 or 3 depending on EX4 or 6. I know Amazon has cheaper ones but these work and readily available.
Amazon.com : Stock Your Home Disposable Aluminum Foil Broiler Pans (10 Pack) - Broiler Drip Pans for Oven - Durable Broiling Pans with Ribbed Bottom Surface for BBQ Grill Like Texture - 13x9 Inch Broiler Pan : Garden & Outdoor