On Ebay American Weigh Scales LB-501 or on Amazon American Weigh Scales LB-501

Was sold out on Amazon for some time but this scale is excellent if you want to mix up to 500g (~300ml in a 100g container). if you don't plan on mixing batches over 120ml (in a container that weighs 50g or less):

American Weigh Scales ACP-200 Digital Pocket Scale, 200 by 0.01 G

is sufficient. I highly recommend the LB-501 though.