How many ways are there to 'always act in the surprise round?'

[Genuine]

Diviner wizards get the ability, as do Sohei monks, and Divine Strategist clerics.

Do any other archetypes get that same ability? Are there any feats, spells, or magic items that do the same, or similar?

[Gisher]

The Grand Marshall prestige class and the School Savant Arcanist (Diviner) get the same ability.

[Cuuniyevo]

Oracle of Time (I recently put one together) can get a Revelation called Temporal Celerity. Once you reach level 7, you may always act in the surprise round, but if you didn't notice the ambush, you act last, regardless of initiative.

If your entire party got the Lookout (Teamwork) feat and stuck close together, it's unlikely that you'd ever fail to act in the surprise round, and that feat is available to every class. It's also nice in that, if you were going to be able to act in the surprise round anyway, you can now take a move AND standard action OR a full-round action instead of having to pick just a move or standard.

[Markov Spiked Chain]

Animal Companion Bodyguard Archetype.

[Kaouse]

A Kensai can act in the surprise round by level 13, and by level 19 he is "never surprised," though little is explained about what that in particular means...

As for spells, I believe there is a spell called Foresight that does this, but it's pretty high level if I remember correctly. There might be a lower level witch version, but that might just be some sort of bonus(/penalty if it's the witch) to initiative I am remembering.

[Damanta]

A hunter with a bodyguard archetyped animal companion after level 3 with the Lookout teamwork feat.

Depending on who the surprised bit is, they might even get a full round instead of a standard action.