An established La Paz operator selling trekking, photography and birding, multi-country itineraries and what they call positive-impact tours. The office is in Irpavi, down in the southern valley well away from the Sagárnaga agency strip, and they see people by appointment only — this is a company that expects to be emailed, not walked into.
They keep a Canadian phone number alongside the two Bolivian mobiles, which tells you where a good part of the business comes from.