What about the "new" ZDZ 40 RE F3A?
It weighs 2 lbs 11 oz incl. the ignition, but without header and pipe.
For comparison, the Brillelli 46 weighs 56 oz (3 lbs 8 oz) including the noise enhancing thingy on the side, which you presumably wouldn't want to use in a pattern model.
ES Composites pipe is 4 oz.

This is probably the lightest gas set-up with enough power for F3A.

Magne