The original recordings were, of course, good old 78rpm records. These are fragile, rare and expensive. Most modern record players don't even have a 78rpm speed setting anyway. Fortunately, some of the greatest collections of the old Rebetiko 78s have been cleaned up and issued on CDs.
LP compilations made from 78s, and original LPs of later period players are also available. They can often be found on eBay (more often than 78s, although these also appear) and sell for reasonable prices.
CD recordingsThere are an enormous number of Rebetiko CDs in existence. Many of these have been made from collections of 78s. The quality of the transfer and cleaning up of the sound can vary enormously. The ones listed below are not a definitive collection, by any means. They are just some of the ones I have had time to write about...
CDs of old Rebetiko
CDs of more recent Rebetiko
Other CDs I happen to like