You do not need an accurate balance or scale to make D-76. Even Kodak, in one of their manuals, wrote that a resolution of + or - 0.1 grams is sufficient. If you visit a sporting goods shop you will likely find a powder balance with that resolution for around 35$. A digital scale may have better apparent resolution, but most recipes are rounded (or should be) to the tenth, and once the slider is set, a deviation of less than a tenth gram shows as off balance. Further, if the weights are accurate and the slider is linear, you know that the weight you are measuring is accurately weighed, whereas the digital scale may have non-linearities that do not show with the test weights.
The teaspoon formula I posted above, as I said, can tolerate at least 1/8 teaspoon give or take in the Metol and Hydroquinone. Furthermore, the volumetric measurements are consistent from batch to batch as long as the consistency of the powders remains the same.