Yea on ebay you should be able to get one for under $15 shipped. They are fine for weighing leos and can weight up to 250-500g accuratly. When you get your scale you can either get a heavy 100 or 150g weight or stack nickels(which weigh 5g each) to check its accuracy. Its best to use a CD case to set the leo on since most scales have a small surface area to weigh on. Just place CD case on then tare weight and place leo on CD case and thats his weight.
What you looking for is somethig that weighs in grams. Postal or kitchen scales would prolly be best. Plenty of options on ebay I did a search once and got hundreds of results and could get a good scale for $15 or less shipped. Most of them were the type you are looking for. Just remember a good scale can weigh 250-500g which is more than you'll ever need to weigh a leo.
This is where I got my scale http://www.reptilebasics.com/store/home.php?cat=258 but I needed a scale that could weigh my adult beardies too so I had to get one that weighs over 500 grams. Its a really nice scale if you're willing to pay the price.