Hi,
have you tried private practices or Rehab Centres? Might be a bit easier there.
But I can also not give you much hope. We have to deal with privacy laws that require each patient to consent to the therapist and treatment; now imagine every patient having to consent to a curious stranger coming to have a look - even if you have the best intentions.
I completely understand you, but the legal implications of simply shadowing a Physio at work are enormous.
Sorry,
Fyzzio