Where can I find the other Channel Divinity options for Clerics that are hinted at in the PHB?

To start, turn to the Feats section.

Feats tagged as [Divinity] expand your options for a 1/encounter Channel Divinity power, such as Ioun's Poise or Raven Queen's Blessing. They aren't cleric-specific; rather, they use the Channel Divinity mechanic to offer a common benefit to all divine characters who follow a particular god. You have at least one feat to spend at level 1, so you can unlock one of these options if it appeals to you.

For Clerics specifically, Divine Power and Dragon 399/400 offer some alternate starting options for your Channel Divinity.

Lastly, any feat tagged [Divinity] will expand your existing options, wherever it comes from. I can't provide a guaranteed complete list of those feats, but each campaign setting comes with a players' guide with [Divinity] feats specific to that campaign's deities, and Divine Power also includes more setting-agnostic [Divinity] feats related to a god's domain.