Yes! I found it! Two hours wasted! Procrastination RULEZ!
Drumroll please................
Bret's lovely guitar, as seen clutched protectively here:

...is a
1974 Yamaha FG 200, as seen here:

This one's varnish is a bit lighter than Bret's, but! It's......is it? Could it be? Yeah! YEAH! I FOUND IT!
You can see that the two thick white lines circling the round sound hole are the same, the chestnut-coloured pickguard is the same, the vintage headstock is the same - oh, I think we've got it.
It's been interesting finding out about this baby, actually. It's not a terribly expensive or fancy guitar. In fact, it seems to have been the first and most basic guitar that a lot of players owned. But Yamaha really seemed to have produced something extraordinarily special in the 1970s. People get a little misty-eyed when they talk about it. Here's one fellow's description of his FG 200:
"It has absolutely beautiful tones and the harmonics really ring out. You can play a harmonic, put the guitar down, come back about two minutes later and it'll still be sending out those amazing sounds! It's true that they don't make 'em like they used to."Or another:
"I've been playing for 31 years, and I've been through many guitars. I have owned 6 new Stratocasters. 2 Marshall stacks. Many assorted pedals. 5 new acoustic guitars. But the only original guitar that has stuck it out with me is my Yamaha FG200.
It's like this: I say play what you got and learn to master it. If you have the opportunity, then move on to other guitars. Like myself, you will find that one special guitar and when you do, you will know it." I really get a kick out of these players talking about their favourite guitars like they're the love of their lives. I don't know. I don't play the guitar. But maybe I just like the idea of having a genuinely moving connection to an instrument like that. I mean, they're inanimate objects, but they're
alive. It's kind of spooky and gorgeous all at the same time, isn't it?
And I love that Bret still obviously adores his old, beat-up friend. He may have other guitars (I've seen him frolicking with a souped-up, top-of-the-line Gibson recently), but his Yamaha is the one he always, always comes back to. There may be fancier and much more expensive guitars out there, but this one? This one is Bret's.
Not sure if the FG200 is the correct model.
Look at the bottom edge of the pick guard and side of the guitar... there is a bigger gap on the fg200 compared to bret's guitar.
Bret's guitar looks more like a FG-170 from the same era.