Thank you all for your suggestions/comments.
I received a lot of help and good ideas.
How I solved this:
I identified the models available and having maintenance/repair facilities in USA/Canada, even if aquired from UK.
I wrote to some manufacturers but not all responded, surprise, surprise.
I decided between:
Kowa 12x50 sv ii (300 USD)
Vortex Viper HD 12x50 (
negociable 559.99 USD)
Maven C3 12x50 (one day special at 360 USD)
The winner is the Vortex, because:
Has the larger FOV,
Probably has the best quality of all 3 models (my opinion). C3 has better transmission, yes.
Probably the best repair service, as I know.
Also, I decided to let my friend choose between the Vortex and a CF Porro binocular.
He will also have the occasion to learn more about binoculars and about his preferences.
I ordered a Nikon 10x50 Action Extreme ATB (36 oz / 1020.6 g - it is more than the 800 g I specified).
I also ordered a tripod adapter.
The Nikon is 175 USD, equivalent for me to a roof at 350 USD.
Both binoculars can be returned in 30 days, just in case I maked wrong decisions.