Okay, here is why it is hard to respond to a request like this.
First of all, top-down view tiles aren't VX or XP or Ace type resources, so they really aren't around here much.
Second, what you are asking for in some ways (or at least in some parts) is very simple.
You can use any old floor tile for the floor (err, duh) and also for the top of the walls. It is just a 32x32 tile, right? (or you could use one anyways. another possibility is to make some cut in half with the outer edge black to more accurately reflect the image you posted.)
So all you really need is four corners and four sides to accomplish the sloping effect.
And there is the rub. Someone would have to make them for you.
But until you go get the exact floor tiles and wall top tiles, they won't know what to make.
Does that make sense?
There are tons of A5 tilesets around. Check them out.
I suggest IceDragon and Aindra, but that's only a beginning.
Good luck!