Hi,
There is no option to do that by default, but it's possible with a small modification and some setup.
So first, you would need to create a new custom field of the table "product" and of the type "dropdown" with two values "yes" and "no" and the column name "canpurchase".
Then, in each product you want to configure that option in the backend and save the product so that the selection is taken into account.
Finally, you want to deactivate the catalogue mode and edit the file "quantity" of the view "product" via the menu Display>Views and change the code:
$this->params->get('catalogue')
by:
($this->row->canpurchase=="yes")