you can do 2 things:
1.) Call coralife
http://www.oceanicsystems.com/, and get another
2.) or by a third party ballast. If magnetic, then just use it... But if electronic, you will need to remove the ignitor module in the unit. The fan is also tapped into the 2 ignitors in the unit, so if you do this, then you will have to rewire the fan to power off something else. No biggie though.
Hope this helps