Windows Store has the Forza Horizon 3 Expansion Pass which includes both the Blizzard Mountain and Hot Wheels expansions for $10.49, regularly $34.99. I already have the Hot Wheels DLC but this is a reasonable price for Blizzard Mountain alone.
Pair this with the Fora Horizon 3 (only) CD Keys deal and you have a good setup.
https://www.microsoft.c