Which vibrator belts work for the tummy?

I want to trim/firm my tummy up and Iv heard that certain vibrator belts work to help firm the belly even though they can be expensive. Does anyone know which belts, website if any & how long it takes to take effect? I'm not trying to loose weight just to firm a lot of skin up since I lost 30lbs already. Pls only reply if you have good knowledge of these belts, thank you.