Here is a more extended version of what I wrote in the camping in Tajikistan article:
The most expensive, but with by far the highest quality, is the small outdoors, hunting and camping store "20 Calibre" downstairs in the Munisa Mall: https://goo.gl/maps/pxrs6unGuuTgtjrw8
They have tents, plenty of camping gas, mountain clothing, hunting gear and most things that you need to survive in the outdoors. The prices are European/American, but so are the products. Everything in the store has a fixed price listed on a tag attached to the product. Tents here sell for $150-300.
The medium budget version is "Varzish Sporttovar" on Rudaki Avenue. It is a collection of independent sellers in one large shop (closed on Sundays): https://goo.gl/maps/rbBtsyrneh9xM1jM7
The quality and prices are at a medium level here. You can find sleeping bags, tents, camping gas and other outdoors supplies. They will be lower quality and heavier than what you find at "20 Calibre." Tents here (a 2-3 person tent) are about 700 Somoni (about $70).
The low budget version is in the Korvon Bazaar. It has no name, but is referred to as the place with sports equipment. Approximate Maps.Me location: http://ge0.me/8zyj0MlPik/%22Sport_tovar%22_camping
We found a random assortment of gear here, including tents that sell for 170 Somoni. These tents are likely only good for keeping the sun off and the mosquitoes away. They are not waterproof and they look like very low quality. I would suggest the tourist stick with the two options above.
The selection, price, quality and range of products cannot compete with what is available in Bishkek. I would strongly suggest buying a tent, sleeping bag and other gear in Bishkek over Dushanbe.