The Slingbox model has nothing to do with it, they all use the same model database for the remotes. And as you say, I am sure there used be at least 002 and 003. I can't check at the moment as I'm in a hotel and the Internet is too slow for Slingplayer, Have you checked the listings thoroughly ?
If you can't find them I did a full set of Custom Remotes for all 8 codes at DirecTV Remotes for Addresses 1-8
On older Slingboxes I could make and choose a different code for Directv, such as for code 00003 instead of the default 00001. I need this ability as more than one Directv in a room and more than one Slingbox. The M1 does not allow any setting, just " does your remote work..." with the default code of 00001 and if I click no instead of a choice it gives an insulting tutorial to plugging in the IR. I could change my IR system and Directv box locations to avoid them interfering but it worked fine with my old Slingbox that died. WHY NO alternate code or ability to change as before ?