The old classic bikes that are popular on the used market right now are often friction shifters. You can narrow down your search by ignoring anything described by vintage, lugged, classic, or any similar words. You'll have a hard time finding a used Cross bike, they became popular fairly recently. Used regular road bikes are moderately common, but might not fit the rack and fenders you want.

In line with RaleighSport, if you are handy, keep an eye out for something you can modify. My commuter began life in the 80s as a MTB, but currently has drops, fenders, skinny tires and is a SS. If not very handy, see if there are LBSs in the area with used bikes, check out any co-ops nearby (although you are likely to get friction shifters there, but they might help you modify a bike you get elsewhere) and check clubs (or LBSs) to see if they know anyone selling used.

Alternatively, reconsider the index shifter/friction shifter requirement. Combining cheap/racks/fenders/light/drops with index shifters that is sorta like a cross bike puts you in a pretty slim market. Removing the index shifter requirement will open up a _whole_ bunch of bikes.

You can find a touring/drop-commuter/cross bike with the features you want, but it may take some patience. Keep looking.