Check out Kleen-Rite's website at https://www.kleen-ritecorp.com. The sell a lot of different shapes & sizes, and you might be able to find a generic one that might work. Door gasket is important for the suction and your customers will appreciate your replacing it!
Thanks. O know KR sells em, as I been washing cars 14 yrs. But i need the specific D/H door gasket
D/H went outta business 20 yrs ago, but still a ton of their stuff around.