Syd, you might want to ask for details from the folks at Anova SUPPORT. Considerate companies make it easy to optimize the use of their equipment. If they mentioned them they might be planning to have them as an accessory or otherwise refer you to a source.
Perforated pans are preferred to roasting on a rack in a pan because they significantly reduce the splatter keeping your oven cleaner. They are also used for combi-oven steaming.
Widely available standard commercial 1/2 size s/s foodservice pans ( 12 3/4" x 10 3/8") will fit your oven. They are made in varying depths, both solid and perforated. The standard 1 1/4-inch deep pans are the most useful. A perforated pan will fit inside your included pan with room to spare, or spend the extra few dollars and get both the solid and perforated standard pans that fit together.
Oh, by the way, to convert inches to metric, an inch is 25.4 mm.