I’ve not really looked yet, but I’m wondering if there are pet stores or exotic pet breeders that sell feeder insects in and around the Taipei area? The reason I ask is I recently got into raising Praying Mantids here in the US and was tempted to continue my hobby in Taipei. I just don’t want to be disappointed to find there is no food supply available locally and watch my pets starve. I don’t really want to bring my own fruit fly or house fly eggs/cultures for obvious reasons, if I don’t have to. Thanks for any input on this topic in advance.
Lots of options in Taiwan’s LFSs. They’ve got crickets, super worms and meal worms. Also, usually 2 kinds of feeder fish, shrimps, baby frogs and even baby soft-shelled turtles as feeders!
And if you plant radishes, lettuce, broccoli, cauliflower or brussel sprouts on your balcony in late March to early May, you’ll soon have a lot of caterpillars for a free daily harvest.
I note though, the OP is looking for small critters like fruit flies. I haven’t heard of mantises being kept as pets in Taiwan, it might be difficult. On the other hand, it’s not hard to raise a crop of drain flies 
Caterpillars start out tiny, like 5mm by the time you see them. 
Hmmm, I was imagining big fat fuzzy things to be sure!
Well, these start out as a white or yellow egg the size of a period, and end up about 25-30 mm long, smooth and green. I don’t know whether they’re on the mantis’s diet, but with three to five pots of radishes you could harvest loads of them every day.
There’s a bunch of pet stores on Hoping West Road Wanhua near the Bangka Boulevard intersection that sell critters like grubs, mice, crickets and such.