Old thread, but I'm adding information as I know several people are searching for impeller replacements for the Vertex Omega 150 (since Vertex is out of business).
I was told from a Sicce USA representative that the Sicce PSK 1000 impeller would work as a replacement impeller for the Vertex Omega 150 skimmer. I purchased the part today and can confirm it fits but have not had a chance to run the pump yet. Note, the PSK 1000 design regarding the wheel part is different than the original impeller but that is basically just a way to break up air into small bubbles (and I suspect the newer design my be better than the older impeller design in that regards).