Taylor, I use a baby scale. The numbers always match up with the baby scale at the vet's office, so I believe it is accurate within ounces.
This is the one I use:
https://www.target.com/p/salter-elec...e/-/A-10019461
I don't recall paying anywhere near that much for it!
Look around for a better price.
Use it on a level hard surface, ideally the same spot for consistency.