If you prefer to book directly via SAS, than call again, and hope to get a better agent on the phone.

I work at a Danish Travel Agency, but not as a TA (but i do have GDS access and skills ;-)), and i had no problem finding that itinerary and pricing it.

But finding an OTA where you can specify mixed cabins is not going to be easy. And SASī own website is not built to book complex itins.