I think, this representation of the alleged V 4 is based on an magazine article or an intelligence report, with no others proofs supporting its reality. Anyway, it surfaced in 1970s in the USA.
Unicraft is known of producing many kits of completely fantasy or fake aircraft - for example Flugkreisels or Kugelblitzes invented by Justo Miranda. ;D
As can be seen, the model is made after an information presented by Mr. Witkowski (who, by the way, has been repeating it in his numerous books for some two decades), who in turn took the drawing from an old edition of a Polish magazine Skrzydlata Polska (Winged Poland). Sadly - as he recently confessed in his book "Projekty badawcze Waffen-SS" (Research projects of the Waffen-SS) - he cannot remember the actual issue of the magazine or any other details. :
The eyewitness report presented by Unicraft from Witkowski's book is of really low credibility. Witkowski often indiscriminately accepts any kind of a report or account, no matter how fantastic they are, supporting his theories. As it was proved by Bartosz Rdułtowski, Witkowski also fabricates completely fake reports or eyewitness statements, building his narration around them. For example, die Glocke is a private invention of Witkowski, as no-one wrote about it earlier, and no sources were presented by Mr. W. other than his words.