Where to setup the List of Vendors that appear in a drop down while entering PR for Released products

Hello All,

While creating the Purchase requisition for Items, Only those vendors appear in the drop down, which are set up as default vendors or the vendors which are mentioned in the trade agreements.

However after submission of the PR, the approver has the ability to change the Vendor.

Is there is any setting or a policy which can be configured, so that even the Submitter can select the Vendor?

Thanks, Kaushik