URGENT!!! need help - shoes for a small size?

I really need help. I need nice dress shoes ASAP. Something conservative/dressy, nothing incredibly flashy...but something that looks really nice. I need a dark colour (black preferred, closed toe, with a heel - not too high (no wedges).
For non-designer shoes, it's VERY difficult to find my size.
I wear size 5 in most American brand shoes (non-designer).
However, I take a size 4 in my sole pair of designer shoes (Ferragamo Audrey). I've tried on Prada, found they run large so...Would size 5 (35) in Manolo Blahnik or Jimmy Choo fit me? What about Christian Louboutin? I don't live near a store that sells high-end shoes, and even then, I find it's hard to find designer shoes in my size anyway! So I must order online. There are no size 4's on Neiman Marcus online that I liked, so I'm hoping a 5 will work. I looked at Stuart Weitzman on Nordstrom online, but I can't remember how SW runs - I tried on a 35.5 once, and it was much too big. I know SW makes size 4, but I didn't like the shoes in size 4 on the Nordstrom site.
Are there any brands/styles/shoes in particular that tend to run smaller? (Since I know it usually depends on the shoe itself).
Can any small-footed ladies help me out? Thanks!