So, I recently purchased a BLOX gold 5 speed weighted shift knob, 450 grams weight (significantly heavier than stock). Now, some may think this might be bad for the trans, but the trans is connected to the shifter via cables if I am not mistaken, so there is no possible problem of having added weight tugging on anything causing wear.
If you feel like the shifting could be smoother, I recommend getting a weighted shift knob. After driving the stock light weight shift knob (es model? dunno if difference than de) the shifts bugged me once in awhile. I would go from second to third and it would feel like it wouldn't go. I am no amateur driver mind you. It was almost like a mis-shift. Sometimes when shifting fast (driving like a maniac!) sometimes it wouldn't go.
After the weighted shift knob install, I have no issues at all at any time. Each gear engages smoothly, quick shift, slow shift, doesn't matter, its smooth as butter. It also has extended the shifter up a little higher since the way the stock shifter screws on and is recessed a bit. I think the only added part the shifter needs is a short shifter....
For absolute, the shift knob you will need is 10mm x 1.25mm.