Is there a way to shorten a telescopes focal length to get a larger field of view?

Answer 1

Yes, there are lenses designed for that purpose. They are called focal reducers/field flatteners. They are primarily used for photographic purposes. Here's a link to one sold by Meade:

http://www.telescopes.com/products/meade-f6-3-focal-reducerfield-flattener-12179.html

Answer 2

Generally not for consumer-level products. You can increase the focal length with additional lenses no the back end.

In order to make a wider field of view, you'd need the optical prescription and add lenses within the telescope, a non-trivial exercise.