Here is a run down on how to do drop shotting
http://www.tacklewarehouse.com/guides/dropshot.html

6" Roboworms are a good place to start lure wise
http://www.tacklewarehouse.com/descpageSFWROBO-RW45ST.html

The M.M. III color is very popular. Oxblood light red flake is also great.

A rattle trap is also called a lipless crankbait. A really good cheap rattletrap type lure is the Cordell Super spot which goes for $3 but catches fish just as good as a lot of $15 baits. Chrome and black is always a good bet color wise
http://www.tacklewarehouse.com/descpageHDLCOTTON-CSS.html

There are quite a few tackle stores around Clear Lake. This website has a good listing of the local shops about half way down the page.
http://www.lakecounty.com/things/fishing.html

I don't know a ton about the different shops at Clear Lake but some of the ones you hear about commonly are Limit Out Bait & Tackle and Tackle It. If you went to those shops, they'd have the right type of lures for Clear Lake.

-Rob