I think 1 gram bars would be good to have on hand. The only problem is the premium that you pay for the smaller sizes. I would only buy if I could get them close to spot. $25.00 plus the shipping if it is fair would not be too bad. With gold at almost $680 as I write this 1 gram would be worth almost $22.00 at spot. I would make sure that they are from a good name mint.
A bank is a place where they lend you an umbrella in fair weather and ask for it back when it begins to rain. --- Robert Frost
I have mixed feelings on the subject. If we have to resort to a gold bartering in the future, the small grams will be needed. I hope things don't get that bad.
On the flip side, if you resell the small gold (to a trader at least), you will probably retain that premium.
I would go with the 1/10 oz coin(or bigger). If it ever comes down to a barter situation the recognizability of coin is/will play a big part in a secure deal. It can be assumed now, at this point in time that a gram bar is real. But if the worse comes to be that may not be true and a big monetary hit will be had in order to cover your bets (So to speak) Plating is simple enough and copper soft enough to work that making a couple dozen to pass off on your way out of whats left of your town would be very common.
Tulving is a good place to get what you need. Darkside stuff is just a couple points over melt.
I got a pamp suisse one for ~20$ on ebay awhile ago when the spot was around 10$/oz. I keep it in my wallet. It's actually pretty cool to have around. I also have a 5g somewhere.