Node Access Product + UC Marketplace
Can you give more detail on the problem and your setup. For example what is a store owner, is this just and administrator of a single site or do you have many store owners on one installation, for example some kind of marketplace?

What do you mean by node access? you want customers to buy a product and then be able to view or edit it.

What version of ubercart/drupal are you using?

If the scenario is you have only one store owner per site and you want a customer to purchase a product and then have view access to a specific node I would look into using the following modules


node reference / entity reference - create a reference to a node from
a product
content access - this allows fine grained permissions for individual
nodes or for content types etc
Rules - create a rule that after successful checkout grants
permission to the node that is referenced on the product