n/s rear indictor not flashing

[volcano rs]

hi i'm new to forum.
i have d3 3.0 tdi quattro sport 2005 .my nearside rear indicator has stopped flashing ,i have tried the one from o/s and it works on near side .it did have a little moisture in there but not too much .
do i have to buy a new light or can i do something with my one ?where is the best place to buy one ? any help is appreciated thanks.