I faced a similar problem when I edited Firesign Theatre's "Duke of Madness Motors"...Firesign famously read out a "Bringing Up Father" strip during an episode of "Dear Friends" (punchline: "Why don't you let him enjoy the war?"). The strip didn't exist in any anthology, so I had to make an interlibrary loan request to San Francisco Public Library to get the 11/18/1918 edition of the San Francisco Examiner on microfilm. It was beat to hell, of course, which meant ten hours in Photoshop to get it to look presentable. Hope everyone's duly infuriated about libraries throwing out their paper holdings. To fuel the fire, why not read Nicholson Baker's "Double Fold"?