Hi,
Go for end cord fastener (used for leather, suede or silk cord). Here's the instruction in case you need it;
First you put all 3 strands inside, then fold this fastener side by side so they overlap each other a little bit or even better if you use crimp folding plier to form the fastener into round-tube-like shap (I wish I had the sample in hand sorry.) The end result/finish looks very nice.
Now, you connect the loop which is on top of this fastener with any clasp you'd like to use.
Hope this helps.
Jack.
PS. I have this 2x2mm. fastener in silver, gold and gunmetal in stock but not yet on our website. If anyone wants to try it, please e-mail me.