Getting engines is easy, it's whole cars that are tricky. The Mazda 20B (3-rotor) has been available for years as a crate engine out of Australia for around $4K, mostly being used by the kitplane crowd with a planetary PSRU and also those wanting to repower the 3rd gen RX7 to it's original domestic specs.
tats a 26b....4-rotors
and sticking a 20b is easier into a 2nd gen then a 3rd