Is there extra-biblical evidence for the Exodus?

I've heard from multiple sources that there isn't even the slightest of (extra-biblical) evidence of the Exodus story or even evidence for the presence of Israelites in Egypt. If this is true, why is this and how do Christians get over this lack of evidence? If this isn't necessarily true, what extra-biblical evidence is there of Israelites being enslaved, escaping, and wandering in the desert for 40 years?