Off the top of my head, I'd say just buy an MX83 Cressida (7M engine) cap and it should fit fine. Ask them to look in the application book for, say, a 1992 Cressida and it should give them the right part number.
I have both (7M and 1JZ Cressidas) in my shed, so I'll have a peek at the caps this-arvo and see if they are the same pressure. I'm 99.9% sure they are the same shape.