[ RadSafe ] HPGe efficiency calibration source for soil samples

[Carl Willis]

Dear Radsafers,

This inquiry is directed toward those of you familiar with
radionuclide analysis of soil or similar samples.  A friend in Japan
has mailed me (in the US) a bunch of soil specimens collected in the
environs of Tokyo in order to determine anthropogenic radionuclide
(e.g. Cs-137, Cs-134) concentrations therein with my HPGe detector.
We both understand this is a strictly avocational and uncompensated
pursuit and that I have no accreditation, nor are my capabilities
likely to satisfy ANSI N42.14---It's basically a hobby.  That said
though, I would like my effort to be as credible as possible without
breaking the bank.  Can anyone recommend a multi-energy source I can
buy off the shelf, license exempt, for calibrating efficiency and
energy (0.2-2 MeV or so), whose physical attributes are a good match
for a few ounces of soil in a bottle?  Any perspectives on how much
such a source costs?  Any creative ideas or tricks for "making" one
using a more-common encapsulated cal source?  Thanks for any ideas.

-Carl Willis
505-412-3277