Finding the right saddle...

[KnottedYet]

While I've never say, measured my sit bone distance, I suspect they are on the narrow side as I have pretty slender hips.

Size of heinie (iliac crest span) has almost nothing to do with sitbone/ischial tuberosity span (pelvic outlet). For example, my iliac span (ASIS to ASIS) is only 12 1/2 inches. Pretty narrow when compared to my ischial tuberosities which are 7 1/4 inches!!!!

Even women with slender hips can give birth...

First thing you might want to do is measure your ischial tuberosities, that will give you a lot of good information to help you on your search.

Next might be a good idea to check out your Q-angle of your femurs, that can help decide if you need a T or Pear shaped saddle. (I've got walloping huge Q-angle and huge long femoral necks) I don't know of a good way to check Q-angle other than having a PT help you. Honestly, I think just riding the two different shapes and comparing them is the best way to figure out the best saddle contour.

Then take the "cut out test" on a hard flat wooden or stone bench.

Those 3 pieces of information will make your search much easier!

ETA: Sarah beat me to it!