Where do I go to download the correct software to do an untethered jailbreak on 4.2.6? I have already jailbroken my iPhone 4 with redsn0w using iPhone3,3_4.2.6_8E200_Restore.ipsw but my mom is making me sell my laptop and I need to find a way to make my jailbreak untethered. 

Is this possible?
Better option if your iPhone 4 is not unlocked would be to update to 5.0.1 and then jailbreak it.  There are untethered jailbreaks available for this firmware. This would give you the benefits and new features of ios5.