The plastic trigger guard is a really nit picky thing people worry about breaking.
I've worked on hundreds of mossberg shotguns. I think I've seen maybe three with broken trigger housings, and those were the ears that locate the front of the assembly into the receiver, not the actual trigger guard.
I've seen far more broken plastic tang safety buttons.
In short don't worry about it, you'll pay as much for the metal trigger housing assembly as you will for another maverick 88.