Stats on registered party voters voting the other way?

Are there stats available to the public on the breakdown of when registered party affiliates actually vote the opposite of their affiliation?

Example: Registered Democrat (who voted Democrat during the last Presidential election) votes Republican during the next election, and vice versa?

This must exist right?

I would hunt around news websites or other election sources and see what exit polling is available.

That’s the only way to determine crossovers.