Some I see that aren't in the list so far...

Wedding gear

The Best Gown Ever (From commendation achievements, the hat can be stored)

1.0 / Mogstation:
Red Usagi Kabuto
Silver Usagi Kabuto
Black Usagi Kabuto
Dream Hat
Dream Tunic
Dream Boots

Enquire Within (I know its not a gear item, but unless you put it in your room there is no where to put it...) Same with holiday furniture like the Christmas trees.

Onion Gear: (As far as I know we could only get these in 1.0??)
Onion Doublet
Onion Gaskins
Onion Pattens

I know I'm hoarding here, but here is the storyline items I have that I can't store anywhere:
(I'm not sure if these can be purchased from an NPC anywhere)

Main Story Quest:
Weathered Shepherd's Tunic
Weathered Shepherd's Slops
Dress Shoes
Dawn Wristguards
Lominsan Ring
Mended Imperial Pot Helm
Mended Imperial Short Robe


Sidequest:
Meteor Survivor Ring