Hi Tait, I hope I can help you with your requests. They aren’t in the original language, but Plough Books has published a series of translations of some of the authors and documents from the various Anabaptist groups that existed during the early days of the Radical Reformation that might interest you. Here’s the link for you to check out. Personally, I prefer to go directly to these publishers rather than buy through a platform like Amazon:
https://www.plough.com/books?tags=spiritual-classics%2Cclassics-of-the-radical-reformation
As for the original language and reading in German, here’s a link to a platform that I personally find fascinating and have benefited greatly from. It functions as a bank of resources on theology, church history, and church practice, and among its resources are quite a few Anabaptist writers and interesting finds. The texts provided on this site are often direct transcriptions of the originals. Here are a few examples:
https://www.glaubensstimme.de/doku.php?id=autoren:i:imbroich:start
https://www.glaubensstimme.de/doku.php?id=autoren:h:hubmaier:start
https://www.glaubensstimme.de/doku.php?id=autoren:m:mantz:start
Leupold belonged to Pilgram Marpeck’s circle:
https://www.glaubensstimme.de/doku.php?id=autoren:s:scharnschlager:start
Kaspar Breitmichel was the first chronicler of the history of the Hutterites and one of the brethren imprisoned at Falkenstein Castle: https://www.glaubensstimme.de/doku.php?id=autoren:b:braitmichel:start
Here in Germany, public libraries have done an exceptional job of preserving and digitalizing original documents and works. You might want to do some research on your own. Here’s a link as an example of one of Balthasar Hubmaier’s writings. Here you’ll face the challenge that German wasn’t yet standardized at the time, and you’ll have to read in a mostly Gothic font:
https://www.digitale-sammlungen.de/de/view/bsb10167959?page=,1
Another resource that comes to mind (also entirely in German) is this website. Among other works and writings, it offers the opportunity to read the Ausbund, the Märtyrerspiegel, and even a digitalized version of the Wormser Propheten. This is Ludwig Hätzer and Hans Denck’s translation of the Old Testament prophets:
https://maertyrerspiegel.de/
Well, that's all from my side for now. Have fun! I am someone who has also recently become interested in the Radical Reformation and the Anabaptist movement.
In the Lord Jesus, a brother by grace from Germany.