Welcome!
I have basically the same light I modified up with a few things. Sounds like you can simply replace the LED/star. It should be 20mm, but I'd measure it first. Best replacement would be an XM-L2 U2 on a copper star, like a Noctigon or SinkPAD. Several places to buy them, depends how fast, how much, where you are...
One good source: http://intl-outdoor.com/noctigon-xm20-mcpcb-cree-xml2-u2-1d-led-p-767.html
Here's a review with some detail info: https://budgetlightforum.com/t/-/17608. It's got 2 wires soldered on - you'd have to remove the connections, ans re-solder the new one. The PCMCB (ie star) is either seated with thermal greasw or thermal epoxy. If epoxied, you simply have to pry it off to break the bond. Clean up the surface well, and re-epoxy with thermal adhesive.