No matter how well-prepared you arrive at Georgia, there is one thing you will probably need anyways as airlines don´t permit it in the luggage - the camping gas. Here is the list places, where one can buy it. I would like to expand it over time, but I will need also your input - if you know some place which is not listed here (I am sure there are many), please let me know and I will add it into the list.
Unless stated otherwise, places I list here sell sealable canisters with a screw on top (such as Coleman or MSR), not the ones which you have to pierce or non-threaded CampingGaz models.
If you are using stove with a spirit burner (such as Trangia), you can find very cheap ethanol in any pharmacy. It´s called "medical ethanol" or, in Georgian, sameditsino spirti.
Geoland - traditional shop specialized in hiking maps, conveniently located in city centre. Now open also on weekends, from 10 am. to 7 pm.
NorthFace - Magellan -
another classic shop. Doesn’t lie in the city center, but is easily accesible by metro (Saburtalo line, Medical University station). Open also on weekends, from 11 am until 8 pm.
Magellan also recently opened another shop at the Tbilisi Gallery mall, close to the Liberty square metro station. You can get there classic Colemans as well as Campingaz canisters.
MPlus - well-equipped outdoor shop located at 25 Vazha Pshavela Avenue sells both standard and Campingaz canisters. Sells also gas stoves, trekking maps and other outdoor equipment.
Sportmaster - located at Miminoshvili street in Tbilisi. Sells Korean-made 'Maxsun Camping' branded camping gas. The small cartridge (230g) cost 16 lari.
Camping gas can be bought right at the airport, as the Georgian Bus counter, right at the exit. They charge 40 GEL for 500mg canister - expensive, but still very convenient to buy it right at the airport.
In case that Georgian Bus runs out of canisters, drivers of marshrutkas serving the airport often have some canisters for sale, too.
Another place in Kutaisi where you can get gas canisters is the hunter's shop Westerni located at the Grigol Robadzikis street.
In Mestia, several souvenir stores along the main street are selling camping gas canisters, both small and big ones. In you are looking for gas for Campingaz stove, try souvenir shop at Seti square 4.
Camping gas can be bought at the Mountain Freaks agency, Mountain Travel agency and Mkinvari Travel agency, all located close to the center of the village.
Canisters can be also often bought from drivers of marshrutkas on Tbilisi - Kazbegi route.
Camping gas can be bought at the guesthouse Old Omalo and maybe also a few others.