Type "star in circle" into Ebay's search and many will come back.
To paint broadly without many specific dates, until the mid-1890s, postmasters of lower classes offices had to buy much of their own equipment, including cancels. The introductory pages of the Postal Guides contained ads for private companies making various cancels for these small offices. There were many town-mark styles and killer styles including stars.
January 1882, Postal Guide (2 images):
January 1887 Postal Guide:
PMG John Wanamaker's business acumen changed a lot of postal operations in the 1890s. Sometime between the 1893 and 1902 Postal Laws and Regulation collective volumes, postmarking devices became issued to all offices:
(1902 PL&R, section 567.4):
Many postmasters continued to use their purchased handstamps until worn out. And certainly exceptions can be found where an old device was called back into service, used at the nixie desk, etc.
Sol Salkind's "U.S. Cancels 1890-1900" illustrates hundreds of fancy killers, many of which were duplexed into these postmaster-purchased devices. And of course earlier, Edward L. Willard's two volume work "The United States Two Cents Red Brown of 1883-1887", and the wheel of fortune cancels discussed in this thread:http://goscf.com/t/70304