Granting a Domain to an Oracle?

[Palanan]

Is there an archetype or feat that would grant a domain to an oracle?

And if not, would exchanging a revelation for a domain be a fair trade?

[Kurald Galain]

Kind of, with the Believer's Boon feat.

And if not, would exchanging a revelation for a domain be a fair trade?

No, since domains generally have two powers and a set of nine bonus spells. Exchanging a revelation for one of the domain's powers would be fair.

[Robster]

Highly specific (and not really what you asked for), but on the odd chance it helps: There's the Pulura's Stargazer prestige class from Paths of the Righteous which grants the Stars subdomain at level 3, along with full casting, a bunch of other goodies (like a familiar and a witch hex of your choice) and having relatively simple prerecs.

[Baroncognito]

So, there's Variant Multiclassing. In exchange for half your feats, when you variant multiclass Cleric, you get:

Cleric

A character who chooses cleric as her secondary class gains the following secondary class features.

Deity: At 1st level, she must select a deity within one alignment step of her own. She gains the cleric's aura, bonus languages, code of conduct, and restriction from casting spells of opposed alignments. She also gains the cleric's spontaneous casting ability, which she can use with any prepared casting classes that have the appropriate spells on their spell lists.

Domain: At 3rd level, she selects one domain her deity grants, gaining that domain's 1st-level granted power, treating her character level as her effective cleric level.

Channel: At 7th level, she gains the ability to channel energy as a cleric of her character level – 6 a number of times per day equal to her Charisma modifier + 1.

Improved Channel: At 11th level, her ability to channel energy improves to that of a cleric of her character level – 4.

Improved Domain: At 15th level, she gains the additional domain power of her chosen domain, treating her character level as her effective cleric level.

Greater Channel: At 19th level, her channel energy ability improves to that of a cleric of her character level – 2.