Converting a circulator into an isolator

HI!!

I have implemented the '3-port circulator' example provided with the rf module and now I want to convert it into an isolator.After some search on the internet I have found that a circulator can be converted into an isolator by making one of the ports of a circulator loaded with a 50 ohm load.

I am stuck at the point that how to make this port loaded?I tried placing a slab of some materials like 'barium titanate' which have good microwave absorbing properties but it didn't work.
anyone here who could give me some hints?

Regards,