MQTT to Google Cloud PubSub republishing solution design approach / pattern

Context

I am designing a solution where I need to ingest sensor data from different types of constrained devices into Google Cloud PubSub.

Pre-Conditions

• These constrained devices only MQTT and only support MQTT over TCP. They do not support MQTT over TLS and can not do any sort of certificate based connection. This rules outs Google's MQTT Bridge which needs a certificate based connection.
• I do have the flexibility of picking the MQTT broker, however.

Possible approaches

• The ideal solution would be to some how still use Google's MQTT bridge without the needs to TLS.
• Otherwise, I will need to standup my own MQTT broker, have a consumer which republishes messages from the MQTT topic to Google PubSub.
• Alternatively, if there a MQTT broker that natively provides a bridge / plugin / republisher to republish the messages to Google PubSub that can also work for me.

Questions

Given the context, pre-conditions & possible approaches.

• Which approach is better?
• Which MQTT broker has capability of Republishing to Google Cloud PubSub?

I would really appreciate any suggestion in this regard.