Okay, maybe I'm missing something.

I was toying with the idea of a summoner with Channeling, but I can't find a spirit that has the power.

Can someone point me in the right direction? What are my options on summoning a spirit to do the willing possession?

The best I could come up with is an Ally spirit, since you can buy extra powers that the spirit wouldn't normally have.

TIA

Channeling is a metamagic, not a spirit power.

channeling is a metamagic not a spirit power so you have to be the one to have it from when you initiate.
Edit: Damn beaten

Sorry- suffering from a bout of vagueness.

I couldn't fint a summonable spirit with the Possession power.

Street Magic P. 34

"Some traditions believe in spirits that are invisible and intangible
forces which project into the physical world through
the power of Possession rather than Materialization. This understanding
of the spirit world is part of the tradition’s lore
and integral to the magics used to summon and bind spirits.
As such, all spirits conjured by magicians of a possession-based
magical tradition replace the Materialization power in the spirits’
statistics with Possession. Otherwise, all normal rules for
summoned or bound spirits remain in effect. For more details
on Possession, see p. 101."

You pick a Tradition with Possession spirits, also in Street Magic.

Then when you summon spirits, the spirits you summon have Possession instead of Materialization.