I use this one off ebay: http://cgi.ebay.com/WEIGHMAX-75-LB-D...item53de63316e
It only does ounces and pounds, but I just convert it to grams online. 50 grams is 1.763 ounces, but I just round up to 2 ounces. I think the scale has an error of +-.2oz anyway. I also use it to weigh packages for mailing so I can print my own postage.
On the other note, I don't think you can get in trouble for just having a scale and hookah. Sure, it can be used illegally, but in and of itself, it is not illegal to possess.