Snap on sell one, but it's not CE approved so they don't sell it here in the UK, although they will sell it in the US, but they won't export it!
Mac tools make one, similar if not the same as the Snap on one.
I bought mine from InternationalTools in the UK, I think it's a Ferret 765 or something.
Not cheap, but in my line of work it will be worth it to have happy customers as it will speed up diagnostic time.
http://www.international-tool.co.uk/products/product.asp?id=3583Im sure you will be able to get those cheaper in the US.
I will warn you, the Snap on one I have used in the past and the brand new one I have purchased, well, they are a little finiky, you have to clean the injector line up with some fine emery and sometimes just hold the Piezo clamp with one hand and use the timing light with the other, but I would rather that than nothing at all.
If you read my link, the adapter has already paid for itself in my eyes as it has saved me from either taking it to a Diesel specialist, or a pissed off customer, luckily customer watched over me and seemed happy that I had got to the bottom of his issues.