In that sentence, you would use demand for.
You use demand for when some entity has want of a resource, as in supply-and-demand economics. Examples would include a high demand for candy canes at Christmastime, or a high demand for beachfront cottages during the summertime.
Demand on is used when a situation is challenging, difficult, or pressure-packed for some entity. For example, at some restaurants, there is a high demand on the kitchen staff during the noontime lunch hour.
In some cases, both could be used, although the meaning would be different. For example:
At tax season, there is a high demand on accountants.
means that accountants work long hours during tax season, but:
At tax season, there is a high demand for accountants.
means that many people hire accountants at tax time.