Interesting as I have had a few worn out workhorses too (those poor horses!)
I can see why these were super useful for you.....and I know the feeling of having a gap.
I am rarely duplicator - I just don't quite have it in me. There are a few exceptions. Like Jenni and others said by the time it comes to duplication I rarely could find the exact same piece. I am not thinking about it because often one is enough until suddenly you don't even have one.....
I think you can look at where and how you wore the sandals eg with these four dresses on weekend or travel days you need to walk alot. And then look for something that fills that role - if not exactly but close.
In my case I have worn out peeptoe sandal boots - they are hanging on but only just. I contemplated replacing with similar ones - that are readily available. But in my case, I enjoyed these because I was relatively early in on the trend.....I feel now it is tail end but still very current. The trendy item would be slides or mules - but I have one pair of slides and mules were a marginal call - I wanted a heel and like to show my toes in summer at times. And my other new shoes were cream perforated oxfords. So I decided on chunky tan sandals. They are definitely October- March shoes (six months) whereas the sandal boots were maybe September-May shoes - but I can deal with that.