Your lowest weight choice is "telepathy"
A step back would be reminding the guides that they are working & carrying the gear is required for those who's voice can't maintain the sound level required. Not just being snarky with that; just perspectiving that the amp is a tool to help them do their job.
I think lighter than that will be a hard find, other than the bull horn idea. The Traynor's battery might be able to be downsized, to save weight. &/or a neoprene strap to help with the weight.
I believe Pignose has/had some battery-ed amps. Or a tiny Roland
guitar combo. Dunno if they'll mic in, but with a small pre-amp might still have the weight below the Traynor.
