At this time it is not possible to restrict a hardware tier to a specific project. However, if you edit the hardware tier in the admin panel you will see a setting at the bottom that restricts the tier to a single organization. See docs here: node pools
If you set the project owner as a member of that organization, they will be able to use the restricted hardware tier. I suggest giving the hardware tier a proper title to remind the user it should be used for one specific project as they will have access to this hardware tier from other projects as well.