Lots of potions works.
The bard, witch, paladin, and inquisitor can also provide some nice back-up healing and are able to use wands. If you give out some extra wands as treasure that might help. If you have access to the 3e
Eberron Campaign book there are things called Endless Wands that are wands usable a set number of times each day. One of those for CLW or CMW might speed healing between fights. (It might also be in the
Magic Item Compendium but I'm not 100% on that).
Also check out the Heal Skill and the Treat Deadly Wounds option. Might need to make some extra healer's kits available but it helps.
Another option is to use Hero Points. These are pretty much renamed Action Points. I believe they're in the
Advanced Player's Guide, but check the SRD. One option lets you just not die. Very handy.
If you use them, I'd recommend getting glass beads or something physical to remind people. And they can help stop sudden death from unluck.
Onto the actual question:
Are there any good mechanics for something like a 4E healing surge? Or another way to heal effectively without divine magic? This is a very combat-oriented AP, so I am a little concerned.
It's not that hard to house rules a Second Wind option into the game.
Given 3e/PF isn't an Encounter based game where you're expected to be full each fight, you don't want everyone healing 1/4 of their hitpoints. It should be a minor emergency heal to keep going, usable every so often.
Let's see, an easy number to remember would be your Con modifier. Another would be the amount you heal overnight (typically your HD/level but some options might change that). It might be good to split the difference, where you can spend an action to regain either your Con mod or HD in hitpoints (whichever is higher). I'd say a standard action to get match Second Wind feel, but if people are getting their butt handed to them a swift action might work as well. Maybe usable a number of times per day equal to half your level (minimum 1) or 1+1/2 your level.
Would require some playtesting to see how it actually handles at the table.
An alternative draws from 5th Edition/D&D Next where Hit Dice are not just something you gain that represents your level but is a spendable healing resource. In addition to everything else Hit Dice do, you can roll that many dice per day to regain hitpoints. So a level 3 fighter has 3d10 Hit Dice they can spend outside of combat to heal.