Can anyone recommend a subscription / recurring payment extension for Magento that can handle bundled / grouped products?
Don't have much idea but found this one which may help you,
Recurring Payments & Subscription for Magento 2 using this extension, the admin of the website will have the functionality to manage subscription & recurring payment for his store's products.
Also, this extension will be highly beneficial for the customers as by making future payments automatic, customers no longer have to log in to their accounts each and every billing cycle.
Hope this solution will be helpful for you, if not then you can contact the support team for further customization to make this extension fit for your purpose.