Here's a weighted sheet holder (or paper weight) that can be filled with whatever you like. Just fill in the contents and then snap on the lid. Highly recommended to seal it with superglue once you've loaded it with sand, BB's or whatever.
Here's a video of it being assembled with coarse grain pink salt:
If you found this useful, please share and be sure to peruse my other submissions which are almost as varied as they are many:
http://www.thingiverse.com/3E8/designs
Enjoy!