A note on the scales: Look for one that will do a tare weight. This is so you can zero the scale with a container on it then add your BP to the container and only see the BP weight. You could always weigh the container separate and do the math after but being able to do a tare weight is helpful.
With out a container good luck getting a good weight. The only thing harder then weighing a BP that doesn't want to be weighed is measuring one that doesn't want to be measured.