Struggling with money for my trip?

Im going to Vietnam with a company called world challenge in the summer and it costs 3 thousand pounds. We are there for 5 weeks, trekking, climbing, doing community and voluntary work, seeing the culture etc. I am having real trouble fundraising, and so have written to loads of companys asking for sponsorship money but so far no one is willing. Does anyone know of any that do, or have sponsored them in the past? Do any of you want to sponsor me? Im desperate :( Ive been working my socks off over the past year, and still have a thousand to go :(

Thanks! :)
Additional Details
I already work two shifts a week and babysit and do odd jobs for locals to get money, but its still not enough :(
And I will write about it; we plan to keep a day to day diary out there :)