I’d just go with a standard 550 grill. But you’d want to do some kind of ducting. A standard 550 grill (if it’s open like mine is) just go into the frunk. Most are simply cosmetic.
IIRC, Sierra Madre or someone offers an aluminum grill in the proper dimensions.
Fibersteel offers them. (S-M lists them as out of stock)
Rusty Tubs lists a fiberglass version, and his website is still up, but I’m not sure if he’s still in business.