I think this is an okay start. Can a more experienced homebrewer please check to see if everything's in order? (I'm especially concerned about the CR!)
Hit Dice: 5d10+20 (48 hp)
Speed: 30 feet (8 squares)
Armor Class: 12 (+2 natural), touch 10, flat-footed 12
Base Attack/Grapple: +1/+2
Attack: slam +1 melee (1d4)
Full Attack: 2 slams +1 melee (1d4)
Space/Reach: 5 ft./5 ft.
Special Qualities: Construct traits
Saves: Fort +0, Ref +0, Will +0
Abilities: Str 10, Dex 14, Con -, Int -, Wis 5, Cha 1
Organization: Solitary or gang (2-4) or troupe (5-10)
Treasure: Half standard
Alignment: Always neutral
Advancement: 6 - 10 (Medium)
Level Adjustment: -
These puppets are the creations of the Skull Kid, conjured forth whenever he blows his horn. They carry out his bidding.
Puppets are most dangerous when they can surround foes, wearing them down with under a barrage of attacks.
EDIT 1: increasing HD from 1 to 5.
I'm not really familiar with this game though. From how I understood the article you linked to, the bad guy can summon these automatons to attack the hero, right? Does this creature have any special powers or abilities that you want it to have?