Yeah, I'm not sure why but IBM removed everything relative to MQTT Java samples. They moved the samples to SupportPac MA9C but now even that SupportPac is gone. You can use any MQTT Java samples you find on the internet.
Note: Shocking IBM MQ v9.2 still does not support MQTT V5. It only supports MQTT v3.1 and v3.1.1.
I have uploaded the old MA9C SupportPac.
Regards,
Roger