I forgot which one I had used, I just had one lying around at the time. I believe the part number is 555t from DEI, dont quote me on that. There are a lot of those things around with analogue adjustments or programmable, some more complicated than others.
I just looked now and if you go to
www.soundgate.com ->Trigger Devices -> Amp Turn-On Delay #TRIGDLYA
Look for something similar to that...