Because I haven't seen anyone post this unit's specifications, and because not all websites selling this unit post its specifications either, here they are:
Koolatron C18 (KN-C18)
Power: 12V, 4.5 A, 60 W (separate 110V adapter required for standard home use)
Range: 18°C (32.4°F) below ambient to 60°C (140°F)
External: 13.97" (W) x 12.59" (H) x 7.48" (D)
When I hear the word replacement, I think of the specifications, features, and price being the same or extremely similar. I think this unit may be more of an alternative than a replacement. It's slightly smaller than the MR-138; it lacks a window; and because it lacks an included 110V adapter, it's a much as twice as expensive depending on where it's purchased.