I've used a number of different ones, generally just something cheap off Amazon. I'm sure there are better choices. Just search crane hanging scale and expect to pay ~ $125-200.

I also have an hydraulic version that is less accurate but can get wet, since there are no electronics. It's still good within a few percent, which is enough for most things.

I saw your recent msgs on riding sails and testing and I saw you mention using a load cell to measure. Would you mind sharing what load cell you used? I've often though about using one as our boat yaws considerably at anchor and I've often wondered just what sort of forces are involved. I've also been curious on just how much force we are able to exert when backing down to set, etc... I haven't find much that looked like it would work so I am curious what you found to use. Thanks.