Are the reaper ones you have from their Deadlands/Savage Worlds line? If not there are a couple in there. The old Deadlands figures by Jeff Valent come up second hand quite often. The undead Cowboys were large for the time so generally unfavourable, now with scale creep they fit in fine with larger figures like Malifaux
Another thing to look out for are the figures from the new board game Shadows of Brimstone. They have some undead Cowboys coming out as an encounter pack in future but the 'Swamps of Death' core box has 12 undead townsfolk in it (3 poses) which scale well with Malifaux although not quite as detailed. You probably don't want to buy the game just for that (although the other figures could also be used for Malifaux) but the Kickstarter doubled the plastics that people got so I expect a fair few will hit ebay as they aren't really needed for the game.