I found this place based on reviews - really delicious churchkhela. I recommend. I don't know if there are Russian-speaking sellers, but you can communicate in English. Prices for a large churchkhela start from GEL 6 per piece.
The seller's girl's rather cold attitude, either she treats everyone like that, or only Russians. She was one of 5 people in Tbilisi who did not speak Russian. It was not comfortable to shop.