There are many shops with slippers in Sunny Beach but exactly for mules i'm not sure.but if u go in Bourgas u will find 100%

Hi, loads of shops and stalls in S.B selling lovely shoes at a great price.

Hi - I'm not sure about Loretta shoes, but I bought some natural leather sling back sandals made by Karyoka and they are the most confortable I have had in my life. I saw them in one shop on the front but bought mine in the market area. It was a big shoe shop and it must have been one of the first shops you see on the left hand side as you walk into the area from the main road behind the bus stops. They had many different styles but can't remember if they had mules. The shop also sold other brands so may have had your Loretta ones. Hope this helps.