Why should you stop a vendor being picked to supply an item ir service? Is there a business need? Companies go for internet based supply-chain solutions – to give you a wide choice. So restricting does not seem to go with the trend.
If you have to limit the use, then you’d need to talk to the Security expert or the ABAP expert to limit the choice. This may be based on the user’s profile. The UGR parameter in a user’s profile, or the user’s org unit, can be used for this,