If the bacon is just for flavor, go for anything that has a lot of umami flavor. If you want it to taste specifically like bacon, you could try bacon salt (I've never had it but it's vegetarian and is supposed to taste like bacon) - but remember that a lot of vegetarians might not want things to taste like meat. Otherwise, there are a ton of options with plenty of umami - for example, some types of mushrooms, ripe tomatoes, parmesan, seaweed (nori), or even straight-up MSG. There's actually a question about vegetarian sources of umami with extensive lists.
If you're looking for a textural substitute too, I'm guessing you've got crispy pieces of bacon. At that point, pretty much anything crunchy/crispy that doesn't clash with your recipe would work, and it can probably be separate from the source of umami. It's hard to say much without knowing what you're actually making, though.
Finally, it's not too glamorous, but if you want something like crumbled pieces of bacon, storebought bacon bits (e.g. Bac-Os) are vegetarian - they're basically flavored fried soy cracker pieces.