You won't find any. You need an overheaad vent.

Dacor stills makes downdrafts that work with their rangetops - their Renaissance line. I don't know if these models would work for you.

ERV3615 and ERV3015 Models
An industry leading 15" High Intake provides exceptional performance in capturing smoke and steam from all of the burners
Infinite Blower Speed Control allows for precise ventilation control for optimum performance and efficiency
Removable Easy-to-Clean Filters capture grease without affecting the airflow
In-Line High Speed Fan, Remote or Cabinet Blower required - sold separately
Compatibility:
All Dacor 36" Gas or Electric Cooktops and Rangetops (ERV3615)
Distinctive 30" Gas Cooktop and Distinctive 30" Rangetop (ERV3015)
Distinctive 30" Slide-In (DR30DI) Dual Fuel Range (ERV3015)

Here is a link that might be useful: Dacor Renaissance Downdrafts

Thanks so much Weissman, I called Dacor and it looks like this might work. I was hoping to find one with the internal blower included instead of buying separately which makes it a lot more expensive. The one I got was $800 and this combo is double. I had hoped not to spend so much on a downdraft but it may be my only choice.