I also have the Pelouze scale referred to by Trailrunner and BrianLe. It was about $25 on sale, but that was almost 5 years ago. Watch for sales at places like Office Depot or similar "big box" office supply stores. Any brand scale that has similar functions (there are quite a few out there) is fine. While the "tare" function is handy, with a little simple arithmetic you can get along without it. An accurate scale is also very useful for postage (saves standing in line at the PO to mail Christmas gifts), cooking from European recipes and for dieting. It's nice for food portions (backpacking or at home)--for example, for my snacks I measure out about 300 calories worth of nuts using the gram option. I agree with Brian that the quick "power-saving" shutoff can sometimes be a pain! On the other hand, I'm still on the original battery.

I have a quite accurate Taylor bathroom scale (at least it agrees with the doctor's office balance beam scale) that weighs to a tenth of a pound. Not good for individual items, but great for weighing the entire pack!

I've had a few times recently when the total pack weight was a couple of pounds less than the spreadsheet total. This resulted in a big panic--unpacking and going through the list once more to see if I forgot something! The problem turned out to be the food. I was using a daily average of ten days' supply to estimate the food on the spreadsheet. The basis for the average was a trip when I took quite a bit more food than I could eat. I've since learned to trust my checkoff on the printed-out spreadsheet--I just go through it to see if I missed a line.

The hanging grocery store scales in produce departments, I've found, are very inaccurate. The accurate (hopefully!) ones are in the checkout line and wired to the computer that now fills the function of the cash register. I doubt that the store will let you use those. I suspect that a small post office during non-busy times might be a better bet. I'm sure you can find a used scale somewhere--just check its accuracy before relying on it.