I'd be surprised if you're able to find a lens that will fit it, and if you do, you may also need to construct your own LED module to house it all.
It might have been easier in the long run to just get a Tri Cree RGB and do the color mixing thing, but I'll keep my fingers crossed for ya.
Did the description tell you what kind of LED it actually is? Do you have a link to the seller?
Should be pretty easy to find a lens for these. It’s an old power led design which was pretty common few years ago (around 2010).
Nevertheless I doubt that top tier manufactures like lumileds/luxeon are still making these. Probably some old stock or a clone based on the old design.
From a performance/brightness point of view, Dann is absolutely right. For a nice bright yellow saber, getting a red green amber Tri-Cree star might be the better option - especially when you’re not familiar with electronics. There are some really good/easy saber related led color mixing tutorials on YouTube guiding you step by step (search for color mixing using resistors)...
Assuming you wired your led correctly (the picture does look like it), you might already have burned it, testing with a 3,7V 18650 cell.
If this is the case, even the current driver won’t help you.
While blue / green / white leds will work for short amounts of time when directly connected to a lithium cell,
some colors like red and (maybe) yellow can reach their maximum current at 2,7V - giving them no chance surviving a direct connection to a modern 18650 cell running at 3,7V...
Nevertheless without a data sheet you can’t say for sure. In case you burned the led there should have been some bright light or flash and a noticeable temperature increase within the led star. So let’s hope for the best!