You can grab a copy here.
Also (in case you didn't know already), issue 5 is online, free to read, and already half-over! Start reading it here.
I'm also currently putting together the first Locus Trade Paperback, which will collect the first three issues of the comic. It will have a lot of extra artwork in it, including all new covers for the three issues, all the gallery artwork in the back of the individual print issues, and 16 pages of rare art from the first Locus webcomic I did, way back in 2001.
Currently, it's weighing in at about 106 pages. It's gonna be grand.
Stay tuned! I'll let you know once it's up for sale.