Available in-game for 10,100 Gold, or in bundles, the cheapest being 35€.
Day 23: Rheinmetall Skorpion – Standard (35€)
https://eu.wargaming.net/shop/wot/main/19601/
Bundle content
- VIII Rheinmetall Skorpion
- Bonus 100% crew
- Garage Slot
- Bonus 25×Missions: x5 XP for a victory
Today’s mission gives 
3 Small Boxes. Damage 2 modules or crew members.