I think this one has me stumped. While I could advise you on the licensing agreement and rights, I can't find the owner of the copyright/trademark.
I checked the US Office of Patents and Trademarks (which is searchable, by the way) and could find no Hedaya.
I checked a general search online and found only two references to Heda ya & Co., aside from the one you mentioned. I have placed the links below. Neither gives any information about the company.
I am assuming that the company went out of business or was bought by another company. However, the rights to the doll design could still be held by some company, so I can't advise you one way or another.
Sorry I couldn't be of more use. I don't even know where you should begin to search the company. Have you consulted with the experts on antique and/or vintage toys and dolls. Some of those dealers have a wealth of knowledge concerning the origins of dolls.
I will opt out of this question, in case another lawyer might be of more help.
Best of luck on your search.