you have two things: maximum weight, and resolution.

i would aim for something like: 5000 grams maximum, resolution 1 gram or 2 grams. that will also work for really small snakes, and even smaller food items. these are quite affordable, even with a high resolution of 1 gram.

chemical scale / kitchen scale sounds fine.

if you just go for a high maximum, resolution may be lower, and you may not be able to properly measure a 6 gram mouse or a 14 gram mouse.