OK sadly looks like plastic trebles, tenors and basses are made my only a limited no of manufacturers. I was disappointed in the Yamahas myself but maybe the bigger ones are nicer. Worth tryng the Triebert I would think.
I've tried the Triebert tenor and bass. They're good instruments for their price - nice low registers on both, upper notes maybe not the same quality but still acceptable. The very top notes on the bass are a bit sensitive - I had to be very careful of my thumb position for top E, F and G.
The Triebert tenor is a little too stretchy for my hands (especially the G and D holes), but that's a personal thing. You can never tell what will suit you until you try it.