After much research I found a rubber strap to fit my Omega Seamaster Diver 300M Chronograph, turns out that the OEM 98000087 strap will fit the watch beautifully with a little elbow grease and manual manipulation. The spring bar will need to be curved, but once on it fits perfectly with no gaps !

 

Beautiful piece and it looks great on the rubber!

 

Bringing this thread back to life with my first post here... Any ideas where to source the 98000087 without going to the Omega boutique?

 

I believe that the 98000085 the correct strap for this case? From memory that’s the one I have...