Anyone know of a way to get a trigger guard assembly for a S&W model 1500 in 270 WIN?

Since the S&W1500 mossberg 1500, howa and Vanguard are the same rifle I would think these would be other options as well.

Try these guys.

Sports World, Inc.
6841 East 41st Street
Tulsa, OK 74145
Ph: 918-742-4027

They are the service center for LSI Howa rifles.

You can also try www.e-gunparts.com should be fairly easy to find that part