The only reference I could find to Pritchard's Crossroads is in a book about the 5th Illinois Cavalry. It includes a map of the area involved in a skirmish that does not appear to involve the 11th and 17th. I did find references to skirmishes involving the 11th and 17th near Mechanicsburg on April 20, 1864, and January 4, 1865, but no description of the actual skirmishes. Here is a link to the book mentioned above:

https://books.google.com/books?id=zcf-MOHN8QUC&pg=PA116&lpg=PA116&dq=Skirmish+of+%22pritchard%27s%22+Crossroads&source=bl&ots=iI806dMOJg&sig=Z6CbS2BR5PpqnADknlxjIFxML9E&hl=en&sa=X&ved=2ahUKEwjtyvbW0JLdAhWr0FQKHRahA7MQ6AEwB3oECAIQAQ#v=onepage&q=Skirmish%20of%20%22pritchard's%22%20Crossroads&f=false