A great place to find 5 volt wall warts is Goodwill or Value Village.  They
usually have a good selection and several 5 volt ones.

Switching power supplies are usually regulated.  Transformer type are
typically not regulated and depend on the correct load to achieve the desired
output voltage.  Transformer types are usually the shape of a cube, and
relatively heavy.  Switchers will usually be rated for a range of input
voltages (i.e., 110 - 240 VAC) and will often be relatively thin or small. 
Many Samsung cell phone chargers seem to show up....which are the size of an
oversize wall plug.

At Goodwill or Value Village wall warts usually cost $2.


Jon

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