They’ll find something. Count on it.
There'll always be a noisy minority on just about any issue, let alone a Presidential candidate, but the bulk of FR will eventually coalesce around the nominee. (Unless that nominee is so offensive to the tenets of conservatism that the GOP itself splits along ideological lines.)
Some may declare they're "holding their noses", or "choosing the lesser of two evils", but they'll still come along. There will be some holdouts, who cite various reasons why the nominee isn't "pure" enough, but they will be the minority.