Hi Vhalan! I had the same problem starting off as a GLD when I started the game at CE launch. This was before being able to search the market wards, which I would recommend.. I believe that shields should be listed in the battlecraft ward.
If for some reason you can't locate one appropriate for your rank there, I did the leg work for you and found the low-level NPC bought one here: http://ffxiv.zam.com/en/item.html?ffxivitem=4100101#Sold_By
After going to that link, you can even click on the NPC's name and it will show you where they are in the city!
Best of luck! Maybe we'll run into each other in game ^^