Ok,, first let me clarify, we are talking about the choke solenoid here, not the starter solenoid. Having said that, I am somewhat surprised at the numbers, and my list of possible resistors just went out the window. So, let's start over.
Resistors are rated and sold by two basic values, Resistance and Wattage. To find the wattage in our choke circuit, we first need to find the current (in Amps). To do that, we use Ohm's Law. It says Current equals Volts divided by resistance. We know the Volts is 12. To find the Resistance, we need to add the resistance of the solenoid, plus the resistance of our added resistor. So, 3.3 + 3.3 = 6.6 ohms. Now we can apply that to Ohms Law. 12 Volts divided by 6.6 Ohms = 1.818 or rounded off to 1.82 Amps..
Now that we know the current, we can find the Watts. Watts equal Volts times Amps. So, our 12 Volts in our example are divided equally between the resistor and solenoid. 6V at the solenoid and 6V at the resistor. 6V times 1.82 Amps = 10.9 or rounded off to 11 Watts. I gotta admit, I'm kind of surprised at that. But anyhow, we now know that our choice of resistors ideally should be 3.3 Ohms and 11 Watts. More Watts' rating is OK, but not less.
Now comes the search. Suppose we can find a 3 Ohms resistor but not at 3.3 We can calculate the resulting voltage at the solenoid by using the above calculations. Total resistance becomes 3.3 for the solenoid + 3 for the resistor = 6.3. 12V divided by 6.3 = 1.9 Amps. The Watts will be a hair more than before, due to the increase in Amps.
So, question becomes what would be the resulting Voltage at the solenoid. Back to Ohm's Law, we know that Volts equal Current times Resistance. We also know that the resistance across the solenoid is 3.3 Ohms. Multiply 3.3 Ohms times current (1.9 Amps) and we get 6.27 or rounded off to 6.3 Volts across the solenoid. That makes a 3 Ohm 12 Watt (or more) resistor well within tolerance.
In the real world, we will probably be purchasing a 50 Watt resistor. As I said, more is better, less is not.
Hope somebody is able to wade through this and understand.
EDIT: I already had to make some corrections to this. I hope I got it right this time.
EDIT, EDIT: Radio Shack has a resistor 3.9 Ohm, 10W resistor item Model: NTE 10W3D9, Catalog #: 55047899 for $1.21 (On-Line only). I haven't calculated the numbers, but for a buck-twenty one, I'd be tempted to try it. The voltage at the solenoid will be less, but if it works reliably, OK. Let us know the results if you do try it.