This has been update to A21 and can be found here:
However, there remains a Known Issue that is on the game developers Known Issues Bug List.
The decorations on the Hell Beast and other vehicles is unable to show because the 'buff' that makes them attach to the vehicles is not functioning in A21.
It has been on the Known Issues Bug list for about 6 months. There have been no updates to rectify it.
It means you will get all the speed, jump, and handling of the Hell Beast but it will look just like a regular Motorbike.