Sort order in saved searches

Hi There

There is a clothing manufacturer who sells items in both adult sizes and children's sizes.

These have different sizing types. For example: adults sizes are measured in 'small', 'medium' 'large' while children's sizes of the same clothing style (white shirt) would be in sizes '08','10'',12','14'

I want a way to sort the sizes in a saved search or report so that the sort order is custom. for example

Item: Size

White Shirt S

M

L

08

10

12

14

How would I create a custom sort order?

The normal sort order in the results tab. i.e.