There are many hanging digital scales on eBay and other online scale stores. Search a bit and you will come across a large variety of scales. You may chose best of them for you.
I am currently using
PS-100CR ( 100lb-x-0.05lb Hanging digital Scale), I use this scale with the help of a 6 feet high stand specially made for hanging the scale. It makes my weighing very easy and accurate also......just hang the scale on the stand and the hang your bike on your scale with its hook and that's it.