Any idea where to find APA102 string lights with C9 bulb cover? Doesn't have to be apa102; any string light with a clock pin (easier to program) would do.
There are plenty of ws2811 based string lights. They typically cost $40 to $50 per string of 50 pixels, including shipping to usa.
But all the apa102 based products I could find are tightly packed light tape. The tapes are great for building large video display, but I'm looking for christmas lights.
Your best bet is probably just to buy a string of color-changing C9 LED Christmas lights and cut off the supplied controller. I've purchased some C7 sets from Costco, but it looks like C7s are available on Amazon and other places. You'll probably have to do a bit of reverse engineering to see what protocol they are using.
It's also possible that the supplied controller used an AVR processor, in which case you could try reprogramming it however you want.
--Doug