I Need A Map – What To Do?

I have had a couple of reviews placed on Amazon for The Spiral Tattoo suggesting that I need a map of the city. Now I would have happily obliged and I have at various points hand drawn maps, and looked for some free piece of software to help me draw a map. But nothing has worked well enough for me to put up here or pass to the publishers to include in the story.

My lovely partner has suggested that I run a competition. Send me your best map of Delvenport and I will, ummm, get it included in the next version? Include your name in the next book? Send you a free copy of The Oaks Grove when it comes out?

So I need advice. What can I use on no budget to produce a good map? Or what would be a good prize for a competition?