The term "Hang drum" is often incorrectly used as a generic term to describe Handpans. As you likely already know, Handpans are musical instruments made in the image of the original PANArt Hang.
The Hang (and instruments inspired by its design) are a UFO shaped musical instrument which is a member of the idiophone class. According to Wikipedia: "Most percussion instruments that are not drums are idiophones". This means that the "hang drum" is most certainly not a drum. Although this instrument is most commonly known to the general public as the hang drum, the instrument's actual name is "Hang". This would explain why the original inventors of this instrument strongly discourage the use of this name.
A more fitting and generalized name for this kind of instrument is "Hand Pan".
In the year 2000, inventors Felix Rohner and Sabrina Schärer created the Hang. It was not until 2001 that Felix and Sabrina introduced the Hang at one of the worlds largest trade fairs, the Messe Franfurt. The Hang went on to become very popular over the years and for good reason.
The Hang is played with the fingers and hands and is actually, according to it's creators is what inspired the name "Hang". In Bernese dialect, hang means hand.
The PANArt Hang is no longer available to purchase. You can still buy them on eBay, however that are considerably more expensive now that they have become a collectors item.
PANArt Hang Manufacturing Ltd (the company responsible for the Hang) decided to discontinue production of the Hang in 2013 to instead focus their efforts on their new instrument, the Gubal.
What in gods sweet grace is a Gubal you might be thinking? It's actually very similar to the Hang yet it has some very distinct differences. The Gubal's opening is at the top of the instrument as opposed to it being located at the bottom like on the Hang. You can check out what the Gubal sounds like here.
In its final generation, before being discontinued, the price of the Hang skyrocketed to $2,600. You can now expect to pay double or triple this amount for a second hand one. Although the Hang had been discontinued, the instrument was (and is) still very much in demand. In fact, even though it was discontinued in 2013, the instrument still continues to gain in popularity.
This demand for a product which is no longer available has encouraged other manufactures to start making similar products.
In 2007 the Steel Tongue Drum was invented by Dennis Havlena. His "Hank Drum" was made out of a 20 pound propane gas tank. The base of the tank is cut off and seven tongues are cut into the drum like slits. The tongues are either tuned by adding weights or by the length of the cuts in the metal. It was inspired by the tone layout of the Hang and also the Tambiro, which you can see and hear in action here. This combination gave birth to the Hank Drum.
This inexpensive method of creating a hand pan has inspired many other Steel Tongue Drum inventors to create their own versions and because of this, the Steel Tongue Drum has become a great and also cheap alternative to the steel hand pans that are now made in the image of the PANArt Hang.
Although you can't buy a genuine Hang from PANArt anymore (because they were discontinued in 2013), you can still by a hand pan online that was made according to the genuine PANArt method, which comes with a certificate of authenticity and a serial number. Tzevaot is one manufacturer that creates hand pans according to this method. It is of my opinion that Tzevaot's hand pans are the most quality hand pan currently on the market. It is also, luckily one of the most readily available.
If authenticity doesn't mean much to you and you just want a great sounding instrument, you might be happy to settle with a hand pan that comes out of Bali. They're considerably cheaper and while the quality is not quite as good as the German made pans, they are still wonderful sounding instruments and are available in many different scales. There is a manufacturer from Bali on Amazon that allows the customer to choose whichever scale they like. Pretty cool.