Hi
I have some items that may be of interest to you. Although can I ask why you are after 2x 4ch relays instead of the one 8ch unit? Do you need to install at different locations perhaps? Also you say you're after the one "4 way dimmer relay" - do you mean dimmer and not relay? And would that be a standard 2A per channel unit? And do those OP units need incorporate network power supplies?
If you haven't already been over the Cbus-shop website (http://bit.ly/1rswtvK), perhaps you can have a look at the specific part numbers needed and update your post.
Stephen