Right had another go at this.
All Russian insurers who do this type of cover have no quoted.
This is probably due to amount of work involved for little or no return for them.
This leaves the border option or a specialist travel broker who does a lot of this type of thing. Unfortunately I don't know of any.
Looking at Campbell Irvine, they seem to specialise in Travel Insurance & whilst this is important the motor side is where if it all goes wrong you will have the biggest cost/legal problems.