This is a tip that might look weird, but I have tried it on my d4 with great results. Buy this
http://www3.towerhobbies.com/cgi-bin...?&I=LXHWN4&P=7
Now, what were the chances that the hinge pins from an american 2wd buggy, would work in the d4...? Well, I own an evader buggy, so I tried the hinge pins. The inner ones fit the d4 just fine! You can check the dimmensions in the towerhobbies site, for yourself.
The rear ones won't bend, like the hb original suspension shafts.
The front ones are a little longer, so here's what you do. Drill the 3mm hole in the front rubber mounts of the front hinge pins all the way through (like in the middle rubber mounts of the front hinge pins). Insert them in the other side of the front suspension brace (from the front, not from the rear of the brace as the instructions say). Insert the duratrax front hinge pins from the front of the suspension brace (you drilled the hole of the rubber mounts all the way through) and secure them with e-clips (the duratrax pins use e-clips, unlike the hb ones)! Now the hinge pins can't float through the rubber mounts, back to the chassis, because they are stopped by the e-clips.
If that's not explained clearly, I could add some photos.