There are some delays are I've not received the replacement (6V) lights yet.
Firstly, I could not return the 12V lights as they were installed on my bike and the cables were shortened. (The shop didn't want the incomplete light back). I have to pay for the replacement light (around €70) and the shipping to Singapore will cost around €60. Considering that there will be exchange rate loses and surcharges to withdraw in euro, I suggested to the shop to send me a Birdy3 mudguard set (around €60) in exchange for the shipping cost, which has to be arranged by me. Instead they treated this as a new order and wanted me to pay for everything. I had to go back to basics, and asked them what caused me to received the wrong item. Was it that the shop placed the wrong order, or was the order correct, but the supplier sent the wrong item. Did the shop double-checked the items before packing up for me?
In the end, the shop offered the following options:
1. They send the 6V light for free, and shipping borne by me.
2. I pay for the 6V light, and shipping will be refunded to me.
3. If I want the mudguards as well, I pay for both the lights and mudguard, and shipping refunded to me.
Now I'm not sure whether should I incur additional costs, or try to modify the existing 12V light I have to run on 6V.
I am willing to consider other lights as well, but have to find a suitable and useful mounting point on the bike.