If it's been lost 2 times and wasn't because of theft I'd get another proper cover and attach some latches to the sides or top and bottom, depending where the stock connectors are. I suppose a cable or chain would work too, but that might not keep it from coming loose, only keep it from falling out. If chain or cable breaks or lets go as it's dangling it will still turn up gone.
Harley Ultra Classic (Geezer Glide) Rider, Retired US Army Paratrooper, fisherman, shooter. Proud to have served, proud of those that still do, or have done so with pride.
2005 National Dolphin 34'