I used to work with instrumentation about 20 years ago, one unit called a "recycle timer" will fit the bill but they are not cheap. They can be programed with independant on off durations anywhere from about 1/10 second to hours.
Here's an example:
http://www.airotronics.com/site/prod...cycle_TGKD.php
I have an old one somewhere in my house I was saving to make a wave maker 20 years ago but be darned if I can find it now
I'm sure there are plenty of instrumentation suppliers locally that can source one but be prepared to pay $150 to $500 for one.