Comments:
15300 from bracelet to rubber strap
Hi
I have a 15300st and I wanted to remove the bracelet & add a rubber strap. Some months back I encountered a picture of someone who has accomplished this beauty. However no details were given on how it was completed or if a standard AP ROO strap was used.
Any help would be great 
You can check with your local boutique
Or AP service center. I don't believe such parts will be available though. The 15300 in steel was of course provided on the bracelet, and I don't think steel strap plots or the rubber strap were ever "officially" offered for it.
rubber strap
check if you can order the plots of the 41mm RO. if they fit you can do a conversion.
i put a Leo messi rubber strap on my 41mm ROC
City of Sails Chrono....
is the way to go....
The rubber strap of this model will fit reg. the width. The plots you will need to do this transformation (longer on the "strap side") unfortunately will sit a little deeper, not in level with the "lug surface", as the dimensions of the cases (15300 vs City of Sails) are not the same.
Hope this helps.
Best,
Jochen