Yes, I'm familiar with the "Power Vision" style power extending mirrors with the accordion bellows. They were discontinued at the end of the 2005 model year.
But DRSMPS's post is still confusing, because it implies that a power fold and power extending switch from GM is available, and I don't think one is. I've never known a GM mirror to have both features simultaneously. Only Ford's "Power Scope" mirrors electrically fold and electrically extend. Those factory mirrors retail for $2,000.00 a pair.
My favorite looking extending tow mirrors on the rounded body style 2000-2007 classic GMC trucks are made by Cipa. Not the clip ons, but the full replacement mirrors. You can see the entire planet earth behind you. I'd post a picture, but every single picture I post on RV.net seems to get deleted without explanation.
Anyone considering adding on an OEM quality, non vibrating, factory looking dual bar towing mirror that matches the rounded body lines of a classic 2000-2006 Chevy GMC truck better than the rectangular style, and offers more glass area and wider vision as well, owes it to themselves to at least look at the CIPA replacement mirror first.
You can order them through the RV.net sponsor (Camping World).
Ok, here's a couple of pics of these bad boys:

Link to page on CIPAUSA.com where these replacement towing mirrors are explained.