It tends to be difficult to get good prices on quantities suitable for DIY projects locally, so AliExpress is your friend.
All cables are snake oil in the sense that the "quality" doesn't matter. Resistance can still change the sound, but cable length and thickness play by far the biggest role here, the difference usually isn't big, and not every headphone is impacted. The guy over at diyaudioheaven actually measures frequency response changes with different source impedances and for most headphones it's either nothing or an extremely minor change in bass response.
And yeah, the independent ground is the important element that makes balanced cables different.