Update iPod touch OS remotely
When you plug in the iPod touch, Alt- or Option ⌥-click the device's "Restore" button in iTunes. This will allow you to choose the appropriate ipsw file to load on the device.

Have someone download the appropriate firmware for your device. Below are links to Apple's downloads of the 4.2.1 firmware.


iPod touch 2G firmware 4.2.1
iPod touch 3G firmware 4.2.1
iPod touch 4G firmware 4.2.1