On the Lightinthebox website I found three types that could be suitable, amongst which this one.
I cut away two straps on the left inside, then one at the left outside, which I cut only loose from the sole and then attached it again inserting a little piece of black elastic. Then I tried them on on a dancing night, and danced 5 hours on them without any pain, and without them falling from my feet!
The only improvement that could be made would be that the width was somewhat bigger. Other shoes I bought at Lightinthebox have a width of 8 cm, and these only 7.4 cm. Because of the very favourable price, I ordered them again one size bigger, hoping the width will be a little bigger then.