Gillette*® make a Gel Shaving Cream Product with a dispenser that can be turned into a simple dummy engine. The cap and dispenser body can be attached to the aircraft using a light ply disk. The nozzle may be also used for rudder pedals or…? The cans come in a variety of colours, I've seen: Black, Blue, Green and Silver. Two sizes are available. I have to think that the guy who designed this dispenser must have been a modeller!

The photograph shows my Hog Bipe with OS 91 FS power on the starboard side, while the port side is powered by Gillette