I am Ashlynn I have UK size 9, so it is European size 43 - I can buy unisex sneakers, etc, but heels and boots are much harder to find.
That is a US 11 I think, that is quite a big size, so I can see how it might be difficult to find them in regular stores, they just keep the sizes that are most popular. You should be able to find them online though quite easily.
I used to have a friend who had even bigger feet than you, before you could buy everything online she had real problems to find shoes in her size, but luckily she lived in LA so she used to go to stores that were designed for crossdressers, she didn't get the biggest choice but she could at least get shoes in her size.