Try contacting Jeff Hendricks on eBay. His Ebay name is jwteamp92zp. He has literally thousands of chainsaws and parts. (He has over 7000 items listed on eBay right now).There is someone somewhere with one. Just got to find them.
Its essentially a helper handle with auxiliary oiler and chain adjuster for a 1939 Disston that would run scratcher chain. My guess is it was for the electric power head.