I would probably go for the "de Sitter universe" as he first presented it in 1917 in his famous at the time but nowadays mostly ignored or distorted three part paper: “A. Einstein’s Theory of Gravitation and its Astronomical Consequences”. In it he describes what he called "model B" universe to distinguish it from the one proposed that same year by Einstein. In this universe you can find the "de sitter effect" which predicted the redshift- distance relationship in a very different light with respect to the way it is now understood,and that Hubble used to explain in several instances his redshift-distance observations. However, it works only as an approximation to a universe like the one we observe in which there is litle matter in proportion to vacuum since "de Sitter universe" is an empty universe with no matter.