The potentiometer idea could work, lets calculate!
Our source voltage will be 5V, so we can make it portable. From the chart we know 3 things, that 32ga straight wire requires 680mA to get to 200C, or 340mA when coiled, and we know that 32ga has a resistance of 10.16 ohms per foot. I don't like how it doesn't mention the length of the wire, I am assuming they are using 1ft, but who knows.
Essentially, we want 1 standard resistor that will limit the current to the maximum needed to make 200C, and then use a pot to go from that maximum to 0mA, and we calculate it using the formula R = V/I.
5V/340mA = 14.71 Ohms
So our minimum total resistance should be 14.71 Ohms. We also have to take into account the resistance of the wire. I figure 6 inches should be good enough, which would give us 5.08 Ohms, providing that nichrome resistance is linear (don't know for sure).
So we need a resistor of (14.71 Ohms - 5.08 Ohms) = 9.63 Ohms, this isn't a standard value, the closest would be 9.1 Ohms. So we have a 9.1 Ohm resistor in series with say a 500 Ohm potentiometer, then the 6 inches of nichrome at 5 Ohms. This will put a maximum of 340mA into the wire, and a minimum of 9.8mA
Next we need to calculate the safe power dissipation of the resistors, we will leave the nichrome resistance out of this calculation. The formula is P = I^2*R, or P = V * I
P = 340mA^2 * 14.71 Ohm = 1.7W
or
P = 5V * 340mA = 1.7W
So it would be best to obtain a 2W resistor and a 2W potentiometer, but 2W potentiometers are expensive, so a 5W will be used instead. Cost is like $4.40 for the 500 Ohm 5W Potentiometer, and $0.25 for the 9.1Ohm 2W Resistor from Digikey, and that is in Canadian prices.
Then you just wire it up like this.
You'll see R2, the potentiometer, you only wire it up to 1 of the side pins and the middle pin, leave the other side pin unconnected. Whichever side pin you use, when you turn the pot fully in that direction, you are turning the resistance down and effectively turning the temperature of the nichrome wire up.
I will see if I can find my thermocouple based circuit and draw a diagram of it.