Thanks! I can’t take credit for the idea. I just wanted to post a photo showing how the Solarforce clip interacts with the larger head of the D1.
Several other members have posted about fitting a ‘captive’ pocket clip on their D4. I liked these as opposed to the ‘clip-on’ clips that others have found compatible.
Here are a few, in no particular order: 
emarkd mounted a similar ‘Overready’ clip
CRX used a ‘PK Paladin’ clip on a D4
noboneshotdog used a Solarforce clip and a copper ‘wave washer’ on a D4
