It's just embarrassing to let people know that I can only play 2/4 or 4/4 after playing it for so many months. Today, I took the plunge to look around and invent a simple one, and then train myself up to do 3/4, finally, I did it so quickly.
To begin with, my self invented one is simplest and could be learned within 10 minutes. I did it myself:
D DU DU or
DU DU D
After a few minutes, you can do it like I did.
Searching around youtube, I found this manageable and nice:
4 (1,3)-2 (1,3)-2
Simple enough, I will try to train myself with that and hopefully got it done within a couple of days.
Finally, I've modified it as follows, could be done within one hour:
(1,4)-2, (1,3)-2, (1,3)-2