I checked as much as I could but couldn't find any Mamas&Papas Armadillo City adaptors online anywhere anymore. There were car seat adapters available before, but it might be the model is not supported much anymore and the adapters are simply not sold anywhere now.
I will suggest one of two things now, first, try to contact any seller of the Armadillo City model around you and ask whether he has/can order car seat adapters for you... The second way is to browse classifieds and find someone selling theirs, used. If nothing works, you'll only have to live with this buggy being only a pushchair, not a travel system anymore.
I wish you good luck!