Or you could just use Leather boots, because they are the darkest color light armor enchantable boots, and they are on your feet so arent incredibly noticeable anyway. Depending on what you want to enchant your boots with, you could get Predator's Grace, they have Muffle and Stamina Regen. I would say Stormcloak Officer Boots too, but they don't count as Light Armor, so you don't get matching set. I think you can also get a light armor Worn Shrouded Hood from the Dark Brotherhood that doesn't have an enchantment? You might consider going for a Dragon Priest mask, probably Krosis, because the only enchant you'd get benefit from on headgear is Archery unless you use magic also. I like the look of the Stormcloak Officer Gloves for an assassin, or you can stick with Ancient Shrouded DB gloves. Out of the vanilla light armors that are enchantable, I think your best bet is some sort of combination of things: I like the Black Elven armor mod and Light Ebony armor mod, and I'll have to check into Sicarius armor, that sounds nice. I feel the same way as you, luckily I am on PC though.

If you are on a console, there is no way to get unenchanted versions of the special armors like Dark Brotherhood, Thieves Guild, Nightingales, etc. As ShadowGambit said, PC has mods for it.

Skyrim assasin armor mod