I picked up an electronic fishing weight scale off ebay a couple weeks back. It has a 50kg limit and a hook to attach to whatever you are weighing.
Only used it a few times but it seems to do the trick. It doesn't have a brand, so it will probably end up breaking on me sometime soon /ubbthreads/images/graemlins/smiliesmack.gif.
Yep I use a Berkely Digital Fishing scale that goes up too 50 pounds. Anything bigger than that and I'll go out of my way too find a scale big enough too weigh it. Think it cost $20 or so and I just keep it in the truck box.