I'd recommend getting this scale from Alibaba:
http://www.alibaba.com/product-detail/T ... hZ7UXL&s=p
Then taking out the load cell from it. It will get you the resolution and the capacity you need. You can then take that load cell and put it into an indicator. The load cell will have 4 to 7 wires on it. Two will be Excitation voltage, two will be Signal voltage (these four are guaranteed). The other three will be labeled Sense or Sen and Shield. Hook it up to a cheap indicator. Anything with RS-232 output. Then you get a USB to Serial converter for about $20. The indicator will output a string with the information from the scale depending on how you set it up.
I work for a scale company and do this on the regular. It's not hard at all and requires very little deep programming. If you need any help, let me know!