I forgot to mention that I have a new toy, namely an account on Authorgraph. This site provides an interface for readers to request electronic autographs from authors, whether to add to their ebooks, or to print out and keep with a print book. And yes, it really is a personalised autograph if you so choose. The author can type a message and then sign their name using a tablet, and the resulting file shows the actual signature process.
It’s funded by affiliate links to Amazon, so you can only request signatures for books available on Amazon. However, you don’t need to have a Kindle to request or display the autographs.
I’ve put most of my titles currently available on Amazon into the system, and you can find my account here http://www.authorgraph.com/authors/bookfetishist should you wish to have a play.