Here's a list I found online that lists every single thing you need to find in order to obtain the MARKHOR rank, along with their locations. The locations are listed in the order you would reach them if you were following the main story path.https://web.archive.org/web/20151105172026/http://www.darths...
Each item includes a link with a screenshot of the general location of the item along with a screenshot of the map where you can find it. It is a very useful tool in finding all of the items. Good luck!
EDIT: It has come to my attention that the site itself isn't available anymore. Luckily, Noir Metalhead
found out that the site has been archived and the solution has been updated with the working link.