Try search more about: hyperbaric chamber, hypoxic room's, altitude tent.

Hyperbaric (altitude) chambers and altitude tents are more for resting in hypoxic conditions, but very common method for training in hypoxic conditions are hypoxic room's equipped with tredmill and ergocycle.

Hypoxic training with mask for this work.

Thank you and Welcome Darko Stojanović and Nelson Kautzner Marques Junior. Great answer for develop endurance the way of adaptation to reduced oxygen in the sea level. Intermittent hypoxic training (IHT), also known as intermittent hypoxic therapy, is a non-invasive, drug-free technique aimed at improving human performance and well-being by way of adaptation to reduced oxygen.

However, to determine if this is the ideal training method for an individual, it helps to learn about its positive and negative implications