According to
ebay FAQ for Product Identifiers:
http://pages.ebay.com/sellerinforma....html#FAQ1-5FAQ: "I sell used/collectible/vintage/one-of-a-kind items—do I have to add product identifiers to my listing?
No. Although we recommend that you use product identifiers whenever possible to maintain search visibility, they are not required for listings of used, collectible, vintage, unbranded, or one-of-a-kind items at this time."
FAQ: "What if I am selling a bundle or group of items that could have multiple product identifiers?
Bundles are defined as multiple different products being grouped together and sold as a single offer.
•If the bundle contains a primary items plus accessories (like a camera plus case and additional lenses) use the identifiers of the primary item and indicate in item specifics that it is a bundle offer
•If the bundle is created by the manufacturer, use the identifiers provided by the manufacturer for the group. For example, a gaming system that includes controllers and other related accessories that usually have a unique UPC applicable to the entire kit.
•If it is a custom bundle of items without a primary item (items have similar relative value—for example, a bundle of DVD movies) use "Does not apply"
•If the offer contains multiples of the same product we refer to that offer as a "lot". Use the identifiers of the item that is grouped and use the lot size value to indicate the quantity in the listing. For example, if you are listing a 12-pack of blank DVDs, you'd utilize the product identifiers from a DVD pack and inter a lot-size of "12" when creating the listing."
Maybe if you still need to use a Product Identifier, you can just copy one off a sheet of self adhesive stamps that he USPS scans when you buy a stamp and use that UPC for all philatelic offerings.