Ertl airplane banks often come in scales useful for 25/28mm gaming. They can be had fairly cheap (I usually pay less than $20 including shipping). The only problems is that they are not all in the same scale with some being too large (1/32 scale). Here is a listing of those in roughly 1/43rd to 1/48th scale.
Lockheed Electra Jr. of the late 30's
1929 Buhl CA6 Spokane Sungod. A strange looking biplane with an enclosed cabin.
Keystone Loening Amphibian. Good for getting you in and out of all kinds of terrain.
1929 Lockheed Air Express. Strangely the Lockheed Vega, a very similiar plane, is in 1/32 scale.
Gruman Goose Amphibian. Came out in 1940, so it is a little late for Pulp but it is the same plane as in the Tales of the Gold Monkey TV show.
1929 Curtis Robin. Another little known plane, but as the choice of Wrongway Corrigan it warrants a look.