Great choice! It is an absolutely stunning watch in the flesh. Unfortunately for me, it looks like a shirt button on my 8.5 inch wrist. I envy those of you whose fit is proportional and I curse Omega for not having made it in 43.5mm.
In spite of that, I keep getting tempted to buy one and I have to look up the picture of it on my wrist to remind me that it's not for me.
As far as a rubber strap, I use the 21mm Aqua Terra Worldtimer strap on my 43.5mm PO and I previously used the 20mm strap of the 41mm AT on my old 42mm PO. They fit fine with the original spring bars. I know they make a 19mm strap for the 38.5 AT but I can't confirm whether it fits the smaller PO.