From personal experience, I like Pepperl + Fuchs, though they re-brand Bihl + Wiedemann.
I don't know where you are, but in the U.S. ifm electronic is ifm efector, and I can't find the Interbus gateway on ifm efector's website.
I don't know about Norgren. I think of them as a valve company, so they may also be re-branding.
Phoenix Contact, of course, is the big player in Interbus. If you like Interbus, odds are you're using something from Phoenix Contact, so it would probably be a logical choice to stay with them. However, I had trouble finding this part on their U.S. website, though it may well exist here.