What's "too old"?
You aren't going to find many (hardly any) Do228s built after 2000, and any that were, like that rather optimistic new gen version, will be grievously expensive as a follow-on to the Trislander.
Good aeroplane though, but the original 228's Garrets (don't know about the new gen's ones) were tetchy and delicate and needed careful handling. If only they'd put PT6s on it - they'd have a winner.