I remember one in Model Builder, a simple design. Standard 2 line handle had a 3rd 'arm' that projected left, from the handle center. Wooden handle was drilled for a 5/16"X5" carriage bolt, which was epoxied thru the hole. Right hand palm went over the embedded convex bolt head, and the middle-and-ring fingers had the projecting bolt shaft between them. The end of the bolt shaft was heated and pounded into a 'flat', drilled and fastened to the 3rd line connector.
A twist of the wrist gave throttle response, with a medium return spring at the engine throttle arm.
I liked this approach, as we were flying WAM then...Those guys were using 2 handles, the second one lined to an eye at the rear of the fuse, then to the throttle arm...to yaw outward 15* when full throttled!
Looked Mickey Mouse to me...