I've used the generic unbranded gear cables for a long time and never had a problem with them breaking at a higher rate than either Shimano or Clarks cables which I also tried. Last at least several thousand miles. They are small and light enough that I carry a spare in my tool pouch but can't remember replacing one on the road. I use bar end shifters so you feel the end of the cable when it begins to fray. The last time I bought them it was a package of either 10 or 12 for around $10 postpaid by a US seller. You could experiment by buying one or two from the ebay sellers in the Philippines
Durable 2M Steel Shift Shifter Gear Speed Cable Line for MTB Bike Bicycle | eBay Two would cost you $1.50 postpaid with a delivery time of about 2 weeks.
The only thing to remember is that these are 1.2 mm diameter cables.
A few SRAM twist grip shifters use a 1.1 mm cable so this will not fit inside the housing. Every other shifter I ever came across and most twist grip shifters use the larger diameter cable. I bought 25 feet of gear cable housing for the rare times when I need to replace the housing as well as the inner cable. $15 for 25 feet of gear cable housing from Niagara Cycle.