Additional cloud storage for Power BI

marksa25,

Are you a Power BI pro user? If so, you can create app workspaces, each app workspace has a maximum 10 GB data storage.

Also you can consider to purchase Power BI Premium capacity node through the Office 365 Admin center, you can also have any combination of Premium capacity SKUs (P1 through P3) within your organization, they provide different resource capabilities. 

Reference:
https://docs.microsoft.com/en-us/power-bi/service-admin-premium-purchase

Regards,
Lydia