New single is listed on Amazon, so you can at least get it there.
Looking at it all, Young Days feels like it was intended to be sold at concerts only. It's not available anywhere online (other than probably auctions) because they didn't even have a distributor for it. They offer photocards and other stuff for mail order at
http://www.tnx.cc/goods/index.htm but not those CDs. So if you don't have a disitributor and you're not planning on selling them online, then that doesn't leave many other options than selling them directly at concerts and events.
With the second single, they picked up another independent label as a distributor (
Japan Music System) but if you look at their stats there compared to
TNX's company stats you can see that they have a third of the capital and half as many employees (12 total) Main benefit I can see with using them is that they've been around 3 years instead of just 3 months like TNX, so should actually have some connections for getting things made and shipped. TNX is essentially a private indie label created by Tsunku, so it can't use all the existing connections that UFA would to get stuff wide distribution.