When I was in the Amalfi Coast in Italy last fall, I made sure to get a pair of custom made sandals from Capri. If you're headed to Amalfi, I highly recommend it - these are by far the most comfortable sandals I own, and knowing they're one-of-a-kind makes them extra special. There are plenty of custom sandal shops in Capri as well as Positano and the surrounding area. You choose your strap color and the jewels you want on the strap as well as the strap design. Then the shoemakers create your custom sandal right in front of you. They cost between 70 euro for a simple pair and around 100-150 for pairs that have adornments. Mine were originally 120 euro, but I was able to haggle the price to 75 euro (score!).
After a month of almost daily use of the sandals, one of my jewels started to detach. I called the shop and asked them how to go about fixing it since I was back in my home base of Florence and wouldn't be returning to Southern Italy any time soon. The shop owner happened to be coming up to Florence later that week, and we met at the train station upon his arrival. He quickly fixed the jewel on the sandal for no extra charge. I was impressed by this customer service! It made my annoyance with the jewel detaching go away.
My friends and I got our sandals from Cuccarullo, located at Via Cristoforo Colombo 36 on the island of Capri. You can order them online, but it seems like the website is a little outdated in terms of sizing options. I'd recommend getting them in person anyways though since they size the sole and straps to your feet perfectly!