Ryan, if you haven't already done so, the ChipGuide / MOGH website has a "Query Facility" that you can use to generate a starting list. It will be state-wide Nevada, not just Las Vegas, and will include non-drop chips of that denomination too, but it's a starting point for you. Most of the $2 chips are NOT drop chips, while the $3 and $4 searches are better targets for drop chips.

The Query link is:
http://www.themogh.org/cg_query.php

Good luck in your search.