Asset Field link to another client

We just moved from ITG and have all of our Vendors created as Clients. Several of our Asset Types had fields that would link back to the Vendor/Client where more specific information could be found. For example in an Internet/WAN asset we had a field that would link to the Provider, where you could get more info on contacts, KBs, notes, etc.

When editing the asset layouts I'm not seeing a Client as an option in the Asset Link type.