For leather, a dark brown or black calf strap. Lots of options out there at <$100. There are several threads on strap suppliers in the stickies.
If you want a bracelet, look for an Omega Beads of Rice bracelet — just do your homework and make sure you are buying the real deal and not a fake. A real one will set you back a few hundred dollars, but you can also find generic ones for substantially cheaper to see if you like the look first. Just look on EBay.
Personally, I’d put it on the BoR. Nice watch, BTW. I don’t know enough about these to say if that’s an original dial or not, but it looks great to me!