Before you go on the search to find examples of research paper prospectuses, you need to fully understand exactly what one is. If you do not understand what they are, how can you be expected to know if the examples that you find are good? The simple answer is that you can't! You need to be familiar with the style so that you can judge what it is that meets the requirements asked for by your professor.
In general terms a prospectus gives general direction information relating to the areas that you will be looking into and the ideas you are going to be investigating. It is also useful to show you which areas of research still need to be completed and what you have done already. There are usually three questions answered within the prospectus:
A bibliography is included with the last question. This can be articles, books, etc. that you have not yet had the time to read, but look as if they may provide some essential information to add into your paper. The average length is normally 1 to 2 pages.
Doing a simple search will return plenty of results that you can browse through. Take each one with a grain of salt unless you are familiar with the source since anyone can post a page on the internet. Check into a few of them to see what elements are common and how they are written.
You can check any university website to get some great examples for free. It may be more beneficial for you to check on the site of the educational institution that you are attending, however. If you use your own school, you will see examples of papers that have already been submitted and graded. This makes it easy to see the tone of voice that the school likes to see, and the format they like to see it in.
This is also a great place to seek out some help. Sites that are dedicated to doing papers for students and charging for them have examples of every type of work that they do - including research paper prospectuses.