Where to find an LED element replacement for a bike light?

There's probably one in that light. Light internals vary dramatically. I'd start at CREE.

You're probably better off buying a new bicycle headlight. Replacing just the LED, if that's what is blown, is a major challenge. It's tiny, difficult to handle, requires a hot air desoldering gun to repair, and is mechanically critical in terms of heat sinking. Flashlight vendors often don't want to deal with these problems, and just buy modules with everything attached, which just drops into the aluminum flashlight body. Something like this: They can also be found on eBay.

If you want to pursue this, I suggest asking the same question in the various flashlight forums: which includes a section on bicycle lighting: I suspect you will be advised that the typical LED flashlight makes a marginal bicycle light due to the beam pattern.

Incidentally, I've found more "broken" 18650 cells than flashlights. The problem is that if the cell is shorted, it will go open circuit and play dead. The CID disc can easily be reset:

I've done it your way, but prefer to use the hot air desoldering station. Floating the LED in a puddle of solder and pushing down so that it's perfectly perpendicular to the PCB is what makes hot air preferable. If the PCB is properly laid out, the chip will also center itself on the pads. Using adhesive makes alignment easier, but it's not really necessary if the PCB pads are properly laid out.

The star is a COB or "chip on board". Available in many shapes and sizes: However, the flashlight variety also includes the LED controller chip and is commonly called an "LED flashlight module":

Well, let's see. The most common LED these daze is the Cree XML-T6. Oh swell, no lifetime numbers. Digging deeper, I find:

However, this deals with mostly with LED lighting, not flashlights. I couldn't find anything that is flashlight specific. All the examples are in thousands of hours. "Once again, per TM-21, the reported L70 lifetime is limited to six times the test duration of 10,000 hours, or 60,000 hours.

For myself, I have yet to burn out an LED on a flashlight or bicycle light. However, I have broken many switches and mangled a few controller chips with my experiments. Eventually, the LED will get dimmer and might be a candidate for replacement.

That's how I killed a few controllers. Learn by Destroying(tm), but it was fun and educational. Latest project is a "flat" flashlight using gutless but cheap LiPo batteries that fits in my shirt pocket, belt, hat, or flat surface.

Some of the cheap flashlights I buy on eBay arrived with the LED solder at an angle. I fixed one by replacing the LED because I made a mess removing the glue. The others weren't centered very well, so reflowed the solder to fix those. I got lucky and there was no glue. I also inherited a bag of loose LEDs which I'm using to make an array of LED's and various other experiments. That turned out to be a rather bad idea because of the lack of suitable cooling. I recently helped a friend built a microscope illuminator, which required a different LED.

Well, that's what I've been calling them for a while and you're the first person to suggest that it's wrong. If it has an LED chip, and it's soldered to a board, it's a COB.

Notice the threaded metal housing around the star/COB/whatever. That makes it a module that drops into a flashlight housing.

Sure. There's no controller on the star/COB/whatever pictured, but I've seen some COB's with controller chips on the back side. Sometimes the controller is near the LED as in: while most of the time, it's located in the tail end switch assembly.

True. I don't know the lifetime of an LED in flashlight service. However, claiming that it's about 50 hrs, without any specifics or references, is not much better. It's not a crime to not know or can't find an answer. Incidentally, if you read my postings, I usually preface my guesses with something like "my guess(tm)". Besides informing the reading that I'm not sure or don't know the exact answer. It's also handy for searching for my own rants at a later date.

No problem. I'll find it eventually. I had to leave to help a neighbor move some furniture around and only spent few minutes digging. I'm having a problem believing that the LED lifetime is only

Cool. I also read rec.bicycles.tech, which sometimes has discussions on bicycle lighting. Opinions on what's important, how bright, battery life, dynamo power, and beam pattern vary radically. I'm interested in what you consider to be important.

that's not what I'm seeing here

Tens of thousands of hours to 70% brightness.