Are you sure it’s not the dash that’s cracked. There are slots in the dash that the visor’s pins and metal clips snap into. I find the majority of the time the leading portion of the dash slot has been broken off by age and/or improper removal of the visor/hood. You could use adhesive Velcro to reattach.
I think I know what you mean, the little "retention" side is thin, only like 4mm plastic. And the metal clips have nothing to clip onto now. What I did was pull the metal clips off the "football" visor and turn them over, so now they grab into the opposite side of the dash side. You need a pliers to pull them off, they grab on pretty tight. You don't even need to flip all of them, doing 2 will probably be enough to keep it secure.