FG-150

These is no replacement that would fit.  Yamaha has a very narrow saddle string spacing of about 1.97".  Most modern guitars are 2.12".  And the saddle slot would need to be in the right place for the intonation to be right.  The only option is to have one custom made, which I could do.  yamahavintagefg.boards.net/thread/319/services-available   Removing and installing a bridge is not easy.  They are very difficult to remove, and usually end up with some damage to the top. 

Almost all vintage guitars have high action, and most nee a neck reset to lower the action by fixing the neck angle.  Most also need at least a fret level to play well with buzzing or dead strings.  I've written an article on "The Benefits of a Neck Reset and Fret Level", but I haven't posted it, I need to make some diagrams.  There's some info here.  yamahavintagefg.boards.net/thread/224/inspecting-new-vintage-yamaha-fg  

BUT!!!  There is a chance the bridge can be humified and glued with water thin super glue.  I've done this many times, but it depends on how far it goes. There's nothing to lose, if it's done the right way.  While I haven't posted an exact step by step on this, but I've documented it within many of the repairs here.  yamahavintagefg.boards.net/board/13/yamaha-guitar-repairs