I seem to recall that pretty much all Terrismen, not just keepers, wore a lot of metal/jewellery, meaning discretion wouldn't be quite as necessary. That said, for discreet metalminds, coins and other metal kept in the coin purse with them, as mentioned above, would work pretty well for anything you don't need to wear constantly, as long as you aren't too worried about losing them (imagine losing your copperminds to a rogue lurcher/coinshot). That said you would probably want at least one sight and one hearing tinmind, a steelmind, a pewtermind and a goldmind on your person in case of emergency, maybe an ironmind as well if you could swing it. earrings would work so long as you don't need to store up too much of those attributes, but for my money, bracers around the upper thighs, piercing the skin so they can resist allomancy, is probably the best way to go. they can be fairly large, allowing you to store a lot of the relevant attribute, they'd be difficult for your average allomancer to detect/affect, and in Terris robes, they would be hidden from view. The coin purse ones, then would be less used but still handy metalminds, like copper or zinc, or maybe tinminds for lesser senses like touch or smell, which you probbly wouldn't use too often, plus maybe some spares of the other metals for good measure.