Iran is a country of counterfeit and imitation products! Original trekking and mountaineering gears are available through official,semi-official and unofficial retailers, however they are more expensive, sometimes up to 30% more expensive than in Europe. The reason is the custom duties and poorly regulated retail market in Iran. So if you are coming to trek you might as well bring your own gear. There are locally made gear such as sleeping bags, trekking poles, boots etc but their standard of quality falls below the European brands something that is disproportionately reflected in their price. One of the exceptions is an Iranian company producing good quality crampons, trekking poles and axes called Haftgohar.
The outdoor gear shops are mostly concentrated in the Moniriyeh street of central Tehran and are open until late at night.
The most widely available gas canister is the Kovea.
https://www.lonelyplanet.com/iran/alamut-valley/activities/caspian-trek/a/poi-act/1561471/1332347 https://www.lonelyplanet.com/iran/alamut-valley/activities/caspian-trek/a/poi-act/1561471/1332347