There are
no magic solutions to this: light hitting your subject from a small light source will
always be hard light.
Since the softness of the light depends on the size of the light source relative to your subject, you have two choices:
A - make your small source into a bigger source;
B - get a smaller subject. Shoot insects.
One of the many solutions involving bouncing light off a larger surface will work. Get a portable surface, like a folding reflector, and bring an assistant if there no nearby walls or ceiling.
Physics is determining this one. No way around it.
---------- Post added 06-08-15 at 02:56 PM ----------
By the way, my favourite solution is a softbox attached to a monopod carried by a young assistant. Use wireless flash.