-The first literary version of this is Le Chevalier au Cigne written in old French from around 1192, which is part of the Crusade Cycle of chansons de geste. From then on there many versions in different European languages were written, a well known English version is the fourteenth century Cheuelere Assigne. In the19th century Rev Sabine Barine Gould features it in Curious Myths of The Middle Ages. Here are a few examples (not comprehensive) of where versions of it can be sourced, I have tried to link directly to the relevant web page on a site where possible.
Online Books-Full electronic copies are available for free online. Here are Internet Archive examples Cheuelere Assigne, Curious Myths of the Middle Ages and a Google books examples Cheuelere Assigne , Curious Myths of the Middle Ages
Online Booksellers-For example Amazon-Cheuelere Assigne, Curious Myths of The Middle Ages and Abe Books-Cheuelere Assigne, Curious Myths of The Middle Ages
Book shops-(you may have to order), you could try finding an independent local bookshop in your area