You can buy Litemania´s C-cell Li-ion Charger
1. Cut a wooden dowel to roughly the size of an 18650.
2. Add a screw (brass, or similarly conductive) to each end.
3. Run wires from the screws to a standard C battery holder - something like this. -You might need a D cell holder to account for the extra length of the AW "C"s.
Ultimately, step #3 is the only necessary one, but the wooden, dummy 18650 helps hold the leads on the charger's contact points.
Member abinok made a run of similar adapters for the Ultrafire WF-139, and I don't recall hearing about any problems with them. His wooden dummy cells were attached directly to the battery holders, but that isn't necessary. The higher charging current of the Pila charger ought to make your set-up an improvement over the WF-139 adapter.