All the sources I found by doing a Google Books search for formyl bromide say that it is unstable a decays rapidly. As analogue, you might consider the Gatter-Koch formylation, which forms formyl chloride in situ (i.e., as a short-lived intermediate in the reaction mixture) as a combination of carbon monoxide, hydrogen chloride, and aluminum chloride and the fact that formyl flouride degrades autocatalytically at STP.