Isn't it fun when your headcanons become canon?
I've always headcanon that Monty's shades and bass originally came from Bonnie, and that turned out to be correct!
We know he "gave" him his base since, well, the fake Monty backstory ride shows Bonnie with his orange bass, and later giving it to Monty.
And, his neon lights, such as the one from Bonnie's greenroom next to his mirror, and the one from Foxy's log ride's sewers when you kill Monty using a Glamrock Bonnie neon (Hah, ironic. He got his REVENGE). Both of those neon lights, show Bonnie with star-shaped glasses. Soo, yeah! Headcanon confirmed.