Keanu Reeves wears an Oris Modern Classic 7490 with black leather strap in the 2005 movie Constantine.

The exact model number of the watch seen in the film and promoted by Oris is Oris Modern Classic 633 7490 4061LS. 

The Oris watch has a round date window at the 6 o'clock position and the numbers 12,3 and 9 on the white dial.

This watch is not in production anymore and very hard to find.

Interestingly, the watch is quite similar to the Carl F. Bucherer Manero watch worn by Keanu Reeves in the John Wick movies, read more here.