Hi Rene,
In addition to the Bata museum, the Northampton Museum in England has a significant collection of shoes and may have information for your researcher. She can reach them here: https://www.northamptonmuseums.com/directory/2/Collections/category/8. Many of the major art museums in the U.S. have significant costume collections that include important shoes and may have some that were entered in Worlds Fairs--she could start with the Met and work her way around the country. There is also an important book about women's shoes published some years ago by historian Nancy Rexford called Women's Shoes in America, 1795-1930 that may offer her some information. And finally, I'd recommend she post her question on the Costume Society of America's Listserv (or find a member to do it for her if she's not a member) where a number of curators will likely see it and can respond to her directly.