When someone gives me armour that I don't want, I sell it. So I sold my Thieves' Guild armour, and now the fence wants to upgrade my armour and I can't sell anything to her until she does.
Where can I buy more Thieves' Guild armour?
Update:
Getting the armor from qasmoke didn't work.
It's been many in-game days and whoever I sold the armor to has had their inventory reset.
Best Answer
Thanks to a useful post on Yahoo! Answers, I realized there's actually three sets of Thieves Guild Armor you can spawn through the console, and the UESP is listing the wrong one. The ones you want are as follow:
I've just confirmed it working. The ones the UESP list aren't visible in inventory view (they do show up in the world, though). I suspect they're meant for NPCs, since many NPCs carry invisible-from-inventory armor. Being different armor, it won't work with Tonilia's quest.
For completeness's sake: