Here's the deal... (I just recently purchased my first rep from DSN)
It's a bit vague on how to contact him, he has no official website, and he knows he has access to some of the best reps so you have to come to him.
Two links that are essential:
His current offerings is a photobucket page FILLED with images. You have to be patient and navigate around to the sub galleries, some of them appear empty but are not. This can take you a few hours...
http://s40.photobucket.com/albums/e230/watchmmx/
His blog page (which is outdated)
http://davidsen-dsn.blogspot.com/
His e-mail address can be found on the blog page...
Remember, he's from Hong Kong, his English is extremely limited so stay straight on point. If he at all gets the feeling that you are getting too picky, he'll sometimes tell you to go elsewhere... Could just be a language barrier mis interpretation problem.
Once you find what you like on his photo blog, let him know and he'll give you a price. Then it gets interesting on how to send him payments, he doesn't accept paypal, but:
Western Union
Moneygram
Wire transfer (bank to bank)
Moneybookers (don't even bother with this crap site, spent two hours trying to figure it out and it just doesn't work.)
Western Union is your best bet, don't forget if you send him funds do it in HK dollars to Hong Kong, not to China (there are two selections.) At one time western union denied me until I used a debit card for some reason.
Ask him to send you pictures of the actual unit he's going to send...
Be patient!