When you're serious about science, United Nuclear - now of New Mexico but soon to be of Michigan - should be your supplier of choice.
Sure, the sell books and fun stuff, but they also sell some stuff that clearly isn't heading to the kids.
The scariest things that they offer are their - surprisingly - the supermagnets found about halfway down the linked page. The magnets are strong enough that these words are among their warnings:
If carrying one into another room, carefully plan the route you will be taking. Sensitive instruments like computers & monitors will be affected in an entire room. Loose metallic objects and other magnets may become airborne and fly at great speed to attach themselves to these magnets. If you get caught in between the two, you can be severely injured. These magnets will crush bones in the blink of an eye....these are not things that I want to be dealing with.
Two of these magnets close together can create an almost unbelievable magnetic field that can be incredibly dangerous.
Of all the unique items we offer for sale, we consider these items the most dangerous of all. Our normal packing & shipping personnel refuse to package these magnets - our engineers have to do it. This is no joke or exaggeration - and we cannot stress it strongly enough. You must be extremely careful - and know what you're doing with these magnets.
Two Supermagnets can very easily get out of control, crush fingers and instantly break ribs or even your arm if opposing poles fly at each other.
A small child recently lost his hand when his father left two # 31 supermagnets unattended. The child picked one up and when he approached the other magnet on a nearby table,
it became airborne and obliterated his small hand.
The DMSO and other chemicals that they sell, on the other hand...or the aerogel...or the tritium light sources...meteorites...glow-in-the-dark paints...
If you need radioisotopes, UN has 'em and a bunch of other radioactive stuff including big samples of uranium metal.
And, seriously, they'll sell this stuff to any schmuck, you or me.
A lot of what they sell is for the explosives, nuclear, and pyrotechnics industries, but that doesn't mean they won't sell to li'l ol' you and me.
And a lot of it is just cool.