Depends on what you are trying to weigh. For smaller weights I would check out stores like Bed Bath and Beyond or Target and look for a digital food scale. They are all pretty accurate. Depends on how accurate a measure you are looking for though.
You can do this with any scale. Easiest with digital. Add the apparatus (in my case a small critter keeper) and tare the scale to 0. Then anything you add (chameleon) will be the accurate weight of only that object.
Another simple option is a classic Pesola scale. These are precision spring scales offered in different weight ranges used to weigh birds or other small critters in the field. You don't need to calibrate, use batteries, etc. Very simple to use and to read. Basically they are small tube scales that weigh something hanging from a clip on the bottom. Hold the scale upright with one hand and clip a twig to the bottom of the scale and weigh it. Then get your cham to grab onto the twig and weigh them together. Or, put the cham in a small bag. Easy peasy. I'll go look for a website source but know that most scientific or forestry supply sites have them.
Found them on Amazon. They are a little more expensive these days but still work just fine!
If you want overkill, you can pick up a laboratory gram scale from E-Bay for a fraction of new prices. I'm partial to German made scales like Ohaus or Sartorius and currently have both with differing resolutions.
In reality though, you don't need a super high resolution scale because it is not critical to know how much your chameleon's weight changes due to aspiration or fecal weight, but to have the ability to do it is pretty cool.
Why not you search on Ebay and Amazon because there are many company which offering animal scales that you need for your measurement in cheap rates. I have bought 2 scale from ebay with a lot of features and really cheap price.
I've been looking at scales and figured that it would be a good thing to have- but I'm thinking that since I'm new to the chameleon thing I probably have no idea of all the reasons to have one- I saw a thread on a bearded dragon thread where the poor girl wouldn't eat but still was gaining weight due to fluid retention - the dragon died but the problem was caught in at least one other beardy by weighing and saved the second beardies life -
What I'm asking in my own drawn out way is, are there reasons that I might not have come up with to get a scale? (and what are they) What do I look for when weighing ?