According to GMPartsDirect, 12645725 was replaced by 12680871 which was replaced by 12698946 which appears to be the current number.
Jegs says that they have 4 of them left in stock.
https://www.jegs.com/i/Chevrolet-Performance/809/12698946/10002/-1
GM dealers and reputable companies listed here have them:
Cancellation Policy. We cannot take back installed or tried parts. We cannot take back used parts. In the unlikely event that a part has been placed on backorder or discontinued, we will do our best to try and find one for you as quickly as possible.
www.ebay.com
Cancellation Policy. We cannot take back installed or tried parts. We cannot take back used parts. In the unlikely event that a part has been placed on back-ordered or discontinued, we will do our best to try and find one for you as quickly as possible.
www.ebay.com
Find many great new & used options and get the best deals for Genuine GM Lifter 12698946 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Not familiar with these companies:
Replaces 12645725, 12680871. Part# 12698946.
www.ebay.com
Genuine General Motors Part # 12698946 (12680871) - Engine Camshaft Follower. VALVE LIFTERS. Cylinder Deactivation. Engine Camshaft Follower. Ships from GM Car Parts Online, Cincinnati OH
www.gmcarpartsonline.com
All of the Amazon ones are Chicom garbage and the reviewers all lost their engines soon after installation.