When doing events you don’t always wear your costume, but it is encouraged to wear 501st clothing – especially if you are helping other troopers.
In the Nordic Garrison we have these racing shirts/bowling shirts that could be used for that purpose.
Front 
Back 
Front chest detail 
Inside the collar 
Left and right arm 
Epaulette
The shirt have many details: The imperial cogs, the garrison logo, the Hoth-like landscape, the slogan, the epaulettes, the Norwegian flag…
Printed on the chest is my name and trooper ID.
It is an awesome looking shirt! But it is made from polyester, so it’s not that comfortable to wear.