Sorry. Just now seeing this...
I don't really have a need for anchors anymore, but in the past, I've found breathing (as you mention) and mantras useful.
Breathing: I don't adjust my breathing; I breathe normally. I count each breath in and out as I exhale, counting to 20 and then starting over. It's a good measure of your distraction by the monkey mind if you suddenly come back to your breathing at find yourself in the 30s.
Mantras: For me, Om has been the most effective, though I've used the mantra in my signature, the Pavamana mantra, Om namah Shivaya, the Jai Shiva Shankara Nataraja mantra, and "I am not the body, I am not even the mind."