I don't think he takes online orders. You can email him but your email goes to someone else and that person may take a few weeks getting the emails to John. You best bet is to write him a letter and send a check. He will respond promptly.
John's manual is one of the best. You may also consider Quinn Jacobson's new book, " The Contemporary Wet Plate Collodion Experience" It is also a very good reference.
Well here it is October 3rd. and I just received John's manual and DVDs. It took only 6 days from the time I mailed the order to him via snail mail! Pretty good from a man with no phone or internet connection! Complete with a nice, handwritten note as well. Highly recommended.