Sponsors could be anyone from your website hosts or webmaster to your dealer giving away a set of tires. Anything for free is good and you can list them as your sponsors. The bigger the list the more sponsors COULD line up.
The benefit for the sponsors is getting listed on your website, flyers etc.
Hope it helped a bit..

sponsorships and other stuff
 

You have a very good vision. The delima is:
(money raised for charity > money spent on the trip) That is, if you spend $8000 on your trip, but raise $4000, it doesn't really make sense.
I suggest doing the trip, planned out WAY in advance, and solicit sponsors for advertising. See if there are local organizations that would benefit from their name on a sponsors webpage. Write a book, or do a slideshow/dinner to raise money. You have to put months and months of effort into this to make it a worthwile event.
Maybe organizing dinner/slideshow presentations with local chapters of Amnesty internationl or whoever along the way.
Before you can legally say you're raising money for an organization, you must get official permission from said organization.

Good luck!

Correct.
My friend Brennan Dates is on a fund raising trip for Parkinson's and it took him months to get things in line. Perseverance and some chance meetings made him raise over $ 40K so far!! Check out his site.
Brennan Dates Fundraising Journey for Parkinson Disease

As an ex-charity fundraiser, myself I wouldn't have any qualms about taking money off your sponsored trip and I wouldn't have qualms about your seeking sponsorship to pay for your trip as well. After all if you didn't do the trip the the charity wouldn't get the publicity and despite what people say about "just giving to the charity instead" it rarely happens. Why? because people don't know who to give to, how to give, or where to give, or just plain don't know the charity.

But it's all about being very clear and very upfront on where the money is going as has been said before. So if you do some sums, and work out costs and realistic income then why not.

Interestingly I found that many companies would happily give a product or service, whilst it tended to be private donations that gained us the most money. So one way to go about it is to use those products/services donated to make more money. In your case it'd be using them, to do the trip to raise awareness and raise money.

But basically be honest, up front, and be prepared to do a lot of publicity work.

To me, it's not about what the sponsor has to say to you, as any money given to them is a $ more then they had at the start of the day.

This to me is the issue, As the one sponsoring you I have to decide if what you are doing is something I beieve in and am willing to give my money to you. There are several causes we give toon a regular basis, but alway directly to the agency, and nver through fund raisers, for that exact reason. We want maximum impact for our dollars given, and not 50 plus % going to the one raising the money for the agency so that they can go about enjoying life. Thats how we give anyway.

What did you decide?
 

All gone a bit quiet, I wondered what you'd decided on in the end?

(says man who is now planning his fund-raising effort for his trip and wants to score £100K)