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I have the Blind Beggar ones. They're rather nice.
Maybe the K9-Attack Dogs from the Wild West Exodus Tabletop are what you are looking for?The game scale is 32mm but I have used those dogs for 28mm Necromunda miniatures without problems as a mechanical dog could be slightly bigger than a usual mutt.
Gringo40shttp://www.gringo40s.com/28mm-robots-scifi.html
There's the rather OOP cyber mastiff from Necromunda, which is very nice.And then there's a cyberdog in Mason's own line, which looks great also...
There's the old Mongoose robo dog: https://www.ebay.com/itm/Mongoose-Judge-Dredd-OOP-Miniature-Robo-Dog-/153226555446