"Sales invoices" to vendors?

Hi!

Our customer is a whole saler. Monthly they distribute a product catalogue to their customers. They offer their vendors to buy advertising space in this catalogue. For this the vendor should be sent an invoice.

There are two standard solution as I see it:

1. Create a new customer record for the vendor and create/issue a free text invoice to the vendor/(Customer). 
   1. Cons: Worst case, one would have to register new customer records for all vendors. Not to mention duplicate adminstration.
2. Use the "one time customer"
   1. Cons: Manuall work filling in vendor data. No follow up, if more frequent than "One-time"

Question: Invoicing a vendor, isn't there any easier ways? 

Thanks,

/E