Scale recommendations 400lbs

We bought a new scale a couple of weeks ago and it is showing huge inconsistencies, I just tried and weighed myself on it and my wii fit, and there was an 8 pound difference. I have weighed myself (twice, to make sure it's right) and then 5-10 minutes later I try again and there usually a 5-10 pound difference (no food, drink or potty trips in between). It's the Conair/weightwatchers brand. I need a scale that will go up to 400 pounds for my husband.thanks for the help!