I may well be wrong, but your picture bears all the hallmarks of a watercolour by the British illustrator Richard Simkins. 1850-1926. As such, it may never have been published in a book. I have a copy of Uniforms of the British Army, W.Y. Carmen, published 1985. The book is a reproduction of his plates in private hands. The collection is not fully comprehensive and regrettably the 28th are not included. I'm sure if you search the web and compare with similar authenticated Simkins illustrations, you may at least have a start in tracking down a copy of the print knowing who it's by.