In addition to the four works listed above, there are two incomplete concerto movements, K. 370b and the Concert Rondo, K. 371, both from 1781 and both in E-flat major, and a 91-bar fragment of the first movement for a concerto in E major (K. 494a), written in 1785 or 1796 (Humphries 2000, 87).
Given the duration of the concerti (no more than 20 minutes each) it is quite common to find these horn concertos on the same CD, or in boxed sets of Mozart's concerti for wind instruments or even all his concerti. The Naxos Records CD Complete Works for Horn & Orchestra includes, besides the concerti, three rondos for horn and orchestra completed by musicologists. When a CD has only one of the horn concerti, it is typically paired with another concerto for a wind instrument also by Mozart.
Humphries, John (2000). The Early Horn: A Practical Guide. Cambridge Handbooks to the Historical Performance of Music. Cambridge and New York: Cambridge University Press. ISBN 9780521635592.