Looks like the brand I used is discontinued, lol. If you go to Amazon and search "led mousepad", you'll find a million. I just made sure to order one with lots of color modes, and large enough to ensure the fiberoptic element would wrap around the entire GT, with some extra.

Here's a link to the battery case:

https://www.amazon.com/DGZZI-Female-Socket-Battery-Holder/dp/B085HLPMRR/ref=sr_1_2

Was pretty simple to do, and is by no means permanent, but it seems to hold up to everyday riding, so far. Super easy to repair if it does get damaged tho...

(also, a seam ripper, for sewing, works perfect for removing the fiberoptic from the mousepad without damaging it)