timer relay with pulsed earth output

I am trying to wire in a heated screen and mirrors. In-order to use the original switch gear I need a timer relay that has a pulsed earth output. All the timer relays I have come across so far are of the positive pulse type. Does a pulsed earth timer relay exist? If so where can I buy one? I plan on using the timer relay to switch a 70A heavy rely to power the screen and the mirror heads. Thanks in advance.

You should be able to find a timer switch that has dry contacts on it - with dry contacts you determine what is switched by connecting one wire on the contacts to your desired source and the other wire to your load. Also, you can easily convert a +12vdc output to a (-) output with a standard automotive relay.Kevin Pierson

Hi Sorry I should have said its a momentary switch and I want to keep the "stock" look of the car. Can you suggest a supplier of the said relays? I am not that great with wiring. So simple terms dont hurt me! Regards

Don't you mean a pulsed input from the momentary switch? In that case a latching relay from Omron to control your main relay. You can configure the switch contacts to be either ground (earth) or pos also the momentary switch.