I have got the Haynes one. I got it from amazon.co.uk for 10 pounds (+ postage - it ended up costing around $45.00 NZ). Unless you can get a second hand one, I don't know if you will get ony cheaper than this.
But...there is a better manual than the Haynes one known as the Bentley Manual. It is available from Amazon.com. It is more expensive than the Haynes one, but definately worth it. ( I don't have a copy of it, but have borrowed one a couple of times, and photocopied the relevant pages a couple of times).
Cheers