I get a lot of questions from folks on how to find a certain shoe. It's great to be thought of as a resource and I do remember a lot of different brands and the shoes that belong to them, but I think there is a belief that I have a possibly secret resource for finding shoes.
Sadly, this is not the case.
If you are asking to find a shoe the answer I give you is going to vary by how "old" the style is. If it's a current or just passed season, I'm going to go straight to Google and/or ShopStyle. When I'm in Google I'll look at the results for Shopping, Web and Images. Sometimes the links vary so I try a few different paths. ShopStyle is a good resource for all the online vendors which are aggregated in once place.
If the shoe is recent, I may check the brand/designer's site, Bergdorf Goodman, Neiman Marcus, Saks Fifth Avenue, Nordstroms, Amazon and Zappos. This is because each store gets different stock, color and sizes.
If the shoe is more than a year out I'll still give a quick search on Google - mostly because some may be in a sale stock or because Australia runs behind us on releases. Shipping may be more costly or difficult but if you really want that shoe, you do what you have to do!
At the end of the day though, I go to eBay - US and UK. When in doubt, that's the place to go and where I'm going to direct you. There are tons of resellers who don't need to clear out their stock like stores do so the styles can "live" and are available to find for far longer. Or you may just be lucky enough to find a one-off of the very shoe you are looking for. I've had that magically happen a few times. Shoe kismet!
So there you go. No secret resource or access. Just patience, time and a bit of investigative work. Now get shoe hunting!