What is an analog multiplexer? Do we have a 2:1 analog mux?
You can use a SPDT analog switch for this.

The Fairchild FSA5157 is a single-supply SPDT switch with a range of 0 to +V, where the supply voltage (V) can be from 1.8v to 3.3v.  The maximum on resistance is 0.7 Ω.  It is rated for a continuous switched current  of 350 mA.



The FSA5157 is available from Digi-Key for $0.78 in single quantities