How to switch Zoho CRM to Ultimate in a Zoho One subscription ?

How to switch Zoho CRM to Ultimate in a Zoho One subscription ?

Hello,

We currently have a Zoho One subscription. This comes with a Zoho CRM Enterprise subscription.
according to several documentations we can bump it to the Ultimate version by buying an addon:
https://help.zoho.com/portal/en/kb/one/admin-guide/managing-zoho-one-subscription/articles/zohoone-add-ons#Purchase_recurring_and_non-recurring_add-ons

and here:
https://help.zoho.com/portal/en/kb/one/admin-guide/adding-apps/articles/zohoone-postpaid-add-ons#CRM_Ultimate_Edition_Add-on

I've tried everywhere to find it and failed miserably (honestly it shouldn't be that hard)
Does anyone know where i could find it ?

Thanks in advance

K.M