My recommendation & currently on sale...
I've searched for a Hannigan-Venture Trike cover. First thing I discovered that most trike covers will not fit the Hannigan-Venture. Others are not felt lined through out. I found one though - from the same company that I bought a car cover for my Z4 a few years ago.
The cover is made/sold by CarsCover.com
Here is info:
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Ultrashield Trike Cover 5 Layer Waterproof with Fleece Line
Hannigan Royal Star Venture Trike Cover - Our Ultrashield Trike cover is specifically designed for the auto enthusiast. Our 5-layer fabric is fleece lined to protect your Hannigan Royal Star Venture's fine automotive finishes. Snow, rain, dew, industrial pollutants, tree sap and bird droppings are kept away from your Hannigan Royal Star Venture's finish. Patented UV Stabilizer "Remafim" is used to ensure a long life. Tie down strap and buckle attached with strap pocket built into cover for easy storage.
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Currently on sale for $119.95 including shipping. These covers are highest quality - thick five layered - fleece lined - I was very happy to find that they made a cover for my Hannigan & doubly happy to find it 40% off!
JohnB