Bandits will have Skooma around but Moonsugar is in generally pretty hard to get a hold of and if you do find it mostly like have to be stolen. Once the quest The Bloodstone Chalice has been completed, one Redwater. The khajiit Caravans sell Moonsugar and sometimes Skooma. The powerful open-source mod manager from Nexus Mods. On occasion you'll find dealers on the road they'll be in ragged clothes and wear some kind of heavy armor gauntlets. Make sure you loot and read the letter that will be considered stealing, read it return to the Jarl and she'll tell you to go to the hide out (Cragslane Cavern) which is pretty close to Shors Stone. You'll find a lot of Skooma and Moonsugar.
Kill the two dark elves collect the keys. Nine bottles of skooma can be found in Cragslane Cavern. As part of the quest The Raid you can find eight bottles of skooma here. Prisoners in Cidhna Mine, a silver mine operated by prisoners in Markarth, smuggle skooma into the mine and use it as a currency. Talk to the Jarl she'll give you the key upon accepting the quest. Skooma can be purchased from Khajiit caravans. She'll tel you that the Jarl has the key to the warehouse where she meets the dealer. Intimidate, bribe or Persuade her to tell you who the dealer is.
When she thanks you exit the conversation then you'll get a message: Find the skooma dealers.
You'll find an female Argonian pleading that she'll loose her job if you don't help her.
