The bezel insert on the PRS-3LE isn't the standard Seiko type of "click in" fitment, it actually sits in a trench machined into the bezel as can be seen from the drawing below.
https://thewatchbloke.files.wordpres...6/prs3dwg2.jpg
What this means is there's not much margin for variance in the inner, outer and depth dimensions of any insert you'd like to fit, it also means removing the old one could be problematical in as much as it could suffer damage during removal so changing it could be a one way street.
The second point is there are no dimensions for the insert available on the drawings available on Timefactors webpages (see below) so for guidance you'd have to hope someone has done exactly the same insert swap that you want to do and has a record of the inserts measurements.
https://thewatchbloke.files.wordpres...6/prs3dwg1.jpg
Alternatively you can measure the inner and outer dimensions of the insert on your watch, estimate the insert depth, then trawl the web for the actual dimensions of various inserts you like the look of and see what comes closest.
Sorry I can't be of any constructive help!