Why can't I find a comfortable saddle?
I'd look into a manufacturer that actually makes saddles in different widths, get your sit bones measured, and try one of their recommended saddles.  Keep in mind that there may be a conversion involved.  I rode the wrong width saddle for a year because I assumed that my measurements should match the listed width of the saddle (not true, the company I prefer has a chart and there is basically an offset, ie my 137mm or whichever sitbones actually use a 143mm saddle, not the 135mm one). Here is an example style size chart.

It sounds like you are looking for a particular width, but there wasn't mention of you having your sit bones measured.  If you've done this, but it hasn't worked out for you, I'd be next wondering about abnormal anatomy.  Just like people have different length arms and/or legs occasionally, perhaps your sit bones are not spaced evenly from your midline and you might need to get some inbetween size to accommodate.  There are companies making adjustable width saddles, so that's also something you could look into.