There are currently three somewhat obtainable heads in the shop. One example of such head is the Head of Considerable Length. It is a special hat with only 30 copies in existence. (The original stock was 15, but was raised to 30 due to popular demand). The starting price of the Head of Considerable Length was 8 before selling out.
The Headless Horseman is currently off-sale. It came out of the Skull Trick or Treat Bucket. Unlike The Head of Considerable Length, it appears under the 'heads' tab, whereas the former is a hat.
The Floppy Head is currently offsale. It was not meant to be released to the public, but because of accidentally leaking the head spacebuilder decided to put it onsale for 2500. Only five people got it, and then a month later it was put back onsale for 2500, adding 7 more sales to the Floppy Head.
There are more heads than there are available in the shop. Most heads are declined, and look like the Headless Horseman. Isaiah owns some of these declined heads. They all have been renamed to "."