A 7-8V string of LEDs with no current limiting resistor or LED driver connected to 12V? Yes, you'll definitely pop it. As to the 10-11V string it's only highly likely that you'll pop it. Depends on how quickly you can shut off the power 
If you're looking for a locally-available solution then you should look for a ~1A transistor (google: transistor as switch) and pulse the current to the LEDs with PWM.