Hi CJ,
The 1951 Golden Flash fuel tank should be mostly chromed with the centre strip and two side panels painted. However during the latter part of 1951 and into 1952 there was a nickel shortage which restricted much of the chrome plating. During this time the chromed area of the fuel tank was painted in Matt Silver.
The knee pads were the older triangular ones.
I don't know where you live but two companies that will be able to supply parts for this model are C & D Autos and Kidderminster Motorcycles, both in England.
Beezageezauk