I use an Escali kitchen scale, rated for 15 lbs. I'm not going to bother finding the URL, google it.

Any kitchen scale that can measure in grams, and is fairly accurate (small increments are best) that is DIGITAL (this is VERY important) will work. Expect to pay $30-40.
My scale will weigh an adult skink, however the whole skink will not fit across the scale. You should experiment and find an appropriate container to work with. Get a scale with a good tare function (The escali is a great model for this).