I afraid that the 2nd, petrol tank shown is not suitable either, it is probably off a 350cc sv which were made to comply with the British weight limit of 224 lbs, these were the models A/31 or A/32 which was built during the "Tartan Era of 1931/32" The gear change was built into the right hand knee pad that bolts to the tank, hence to bolts fixings for the gear change gate on the right side from of the tank. For 1932 the same tank was also used on the B/32 which was the slightly heavier 350cc sv, which in that year had lost it sump under the engine. Also the C/32 - Bulldog, which was a light-wieght 500cc which used the 350 cc crankcases and crankshaft but used cylinders bored to 72 mm from memory give near enough to 500cc. The tank you are looking for is physically the same dimension as the first tank you photographed, but with the 2 caps, one for petrol and one for the seperate oil compartment which is built into the tank in a similar manner to the second tank shown.
Just a thought some 250cc and 350cc models around 1934/5 were fitted to a similar style tank as E/29 and F/29 models, i.e. with an oil compartment, and had a gate gear change on the side of the tank, and probably just as rare as the tank for the 1929 models. These were used for a short while before the more bulbous style of tank came in in 1935 that is associated with the later Aero models
Cheers and Good luck with the restoration.