Originally Posted by Matt Syson
Either a google search or Pro audio DIY?
How about a speaker with a rod glued to the coil cap (metalic cap type).
A solenoid with a pole piece that is reduced in size to stop it from rubbing may give some effect but probably limited in the HF response.
The solenoid would need a magnet in place of the plunger, else the motion would be pulling (or pushing) on both halves of the driving signal.
Having considered the DIY plate reverb questions myself, the "rod glued to diaphragm" approach sounds like a good one. I had considered a PA horn driver as the actuator, using a rod epoxied to the diaphragm on one end, and epoxied to the plate on the other. For a pickup, a stereo piezo phono cartridge would probably work nicely, both channels wired antiphase to pick up the vertical mvement at the stylus. These are cheep enough you could probably use several at various places about the plate.
One thing about these DIY projects, just like traveling, there are many ways to get there, and roads girdle the globe. Hope this route helps to get you somewhere.