If you absolutely must have an untethered jailbreak at this very moment, there is always the option of downgrading back to iOS 4.3.3.
Assuming you saved your SHSH blobs for the last firmware susceptible to an untethered jailbreak, you can follow this video tutorial and downgrade to iOS 4.3.3 in about 10-15 minutes. Inside we show you how, step-by-step...