Parabellum makes a shield specifically for the PD. The model is the Sport Shield (SS)and the make a smaller and larger (touring) version for the PD. I cannot vouch for the quality of this specific product (no personal experience), but parabellum has a good reputation, and their products are definitly not low end.
I am sure there are other generic shields that could be modified to fit, but the mounting would likely be a hassel. I think a slick, easy to remove mounting system is a real benifit. I have found removing the shield (if possible) a nice feature for rougher off road riding, where you want to have a good clear view directly in front of your tire, and nothing else to whack into as you jostle around (or is it just me that does that?).
[This message has been edited by Timo (edited 13 August 2002).]