Purchase requisition(new) Redwood page customization - hide a source type option

Hi all,

This purchase requisition(new) is redwood page which is under procurement. Here i need to hide the "Supplier" option under the "Select the source type".

so in Source Region there is two fields- "Custom", "Source Type Code". If i hide both of these or one of them, both option becomes hidden. But i need to hide only one option (Supplier).