Big acrylic Lichtenbergs like these are rather expensive, but as I mention in that old post, you can buy smaller ones from Bert Hickman for quite reasonable prices. They've gone up a bit since I last bought one, but US buyers can still get a small one on eBay for $US31 delivered; there are some pretty affordable ones among the expensive monsters in Bert's Web store, too.
Budget another few bucks for one of those little LED display-base things (an acrylic Lichtenberg doesn't look very impressive unless properly lit).
This outfit also sells Lichtenberg figures online. Well, they would if they weren't out of stock of all of them :-).
Though I doubt even today's 1000+ Watt PSU's could handle this
It's not the power that's missing, but rather the voltage. He uses a 5MeV electron beam, and according to this page chez boeing it can generate up to 10mA. That would give an output power of about 50kW, so in theory you're only about an-order-of-magnitude-and-a-half off. However, a multi-MeV accelerator isn't something you build in your garage.
I must admit that I still find it hard to accept that the electrons would just sit there inside the block. I would have thought that they would at least migrate to the edges, and cause some corona effects in the corners or something. But apparently they just distribute evenly in the medium! Sounds like I still have a thing or two to learn about high-energy physics.