I want an extension which allows my customers to select specific purchased products in Magento 2
Can anybody help me? thanks in advance!
Perhaps, you mean something like the Subscriptions and Recurring Payments extension allowing customers to purchase subscription products regularly.
Here are the modules for Magento 1 and Magento 2:
Subscription & Recurring Payments for Magento 2 - https://goo.gl/Bu4t4g
Subscriptions and Recurring Payments for Magento 1 - https://goo.gl/N3h9Tq
You can consider using Magento 2 Reorder Product. The extension helps customers to reorder previously purchased products quickly in their Accounts.
Let's check demo of Magento 2 Reorder Product for more useful features.