Not sure if VW is going to introduce a OEM Replacement for its original Bicycle Horn? For a Vehicle its size, its simply ridiculous and unsafe. Sounds like they probably used a Single Horn instead of a Dual Low and High Pitch Horn.
Since its a VW product, I do not see why you cannot use a horn combo from an Audi or VW vehicle. If the original horn is a single unit, you might need to change the relay and fuse rating to allow for dual units.
I'm really surprised that the NHTSA hasn't set some minimum standards for Vehicle Horns. A certain minimum level of Decibels should be required as a safety function other then lowering your window and screaming!