The Flolight Daylight Spot LED panel was the first battery powered light I ever used that could make a real difference acting as a fill light in direct sunlight. Up until that point, the only way (aside from a flex fill) that one could light outside was with an HMI, and that meant wall power. So the panels were great for that purpose, but hard to use in other situations without gelling them. Since they output no heat, we usually just taped standard CTO and diffusion to them.
They did have slots for drop in “solid gels”, but once they inevitably got lost, it was hard to replace them.
On my way out the door on my last day at NAB, I came across a company called Cotech Filters. They look like they have a complete line of those solid filters, and not just CTB/CTO/Diffusion either. I don’t know much about them other than that, but if you’re looking for that specific product, hopefully this helps you out.