Thunderbolt 3 to Thunderbolt 2
There isn't really many alternatives on the market. USB-C to Mini DisplayPort exists, but not many with Thunderbolt 3/2 support.

Apple makes a Thunderbolt 3 to Thunderbolt 2 which is supposed to be bidirectional (read more in this support article). In that case you would probably need a Thunderbolt 2 male-to-male cable, but it should work in theory.