I am new to .net, but registered as I had seen my name mentioned on a post about tank straps.
The update on them is that I have manufactured replacement sets and they are now available.
The set comprises of the two straps, fitted with rubber cushioning and the cable clips. There is also a basic fitting guide.
As you are probably aware, the original BMW straps are no longer available, and when they were, the rear beam had to be removed to install them.
My replacements only require the removal of each of the rear wheels in turn, as each strap is made up of two parts.
The price per set is £65.00 plus £7.00 postage in the UK ( Royal Mail 1st class parcel, tracked and signed for)
These are currently only for Z3 versions, but I am working on a modification to cover the Z3M, which has an additional lower canister strap that is bolted to the underside of the smaller N/S strap.

Update......Z3M version now available but limited stock. Of the 15 that were modified there are now only 7 sets left
The price per set for the Z3M version is £90.00 plus £7.00 postage in the UK