The best option for the Yamaha YZF R125 is our Fork Stem Mount. However you'll need to replace the Top Yoke Nut with an open nut like below. Google Top Yoke Nut for - R125 to find shops which sell the nut you'll need. We'd recommend taking your bike to a dealer or service shop to have the nut replaced as it requires a large socket and needs to be torqued up to the correct settings. 

So you can go from this...

To this.