One day I stumbled upon these for 125 SEK.They had an ugly plastic buckle, but I started with removing that one. Then I discovered that the straps were asymmetric, one long and one short.
I cut off a piece of the too long strap, and simply used superglue to attach it to the shorter one. Then I folded both straps into the shoe and attached them to the side with more superglue.
There are no pics of the heels, and I like them because of the shape, but it's visible that they are built up from several layers of plastic. Still I don't think anyone is going to crawl on their knees and judge the shoes that closely. They still look better than my folk costume shoes toegether with my historical gowns.