You're right -- a quick search turns up almost _nothing_ for me. I used to use plastic (and wood) templates all the time as a kid, and still use them occasionally.
Of course, cutting a template out of relatively thick cardboard shouldn't be too bad (one could trace around the parts cut out, if the inner corners are difficult to get right), but an alternative occurs to me: Get one of the standard templates which contain rectangles or non-right-triangles, and _fill_in_ those parts of the template which you don't need (at minimum, a straightedge taped across a rectangle's diagonal would provide a third edge to trace along), perhaps with that same thick cardboard. Those equilateral triangles could do double duty as 30-60-90 templates.
The ideal is to find a young person whom you can trust with a razor blade and some cardboard, and let them go at it.
/************************************
Down with categorical imperative!
flutzpah@yahoo.com
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________________________________
From: Anthony Lapinski <Anthony_Lapinski@pds.org>
To: phys-l@carnot.physics.buffalo.edu
Sent: Tuesday, March 31, 2009 7:46:15 AM
Subject: [Phys-l] stencil
I am looking for a stencil/template to draw (the old-fashioned way) small
right triangles for various physics questions. I already have stencils for
circles. ellipses, and squares. I checked online and in various math
catalogs with little success. Some equilateral triangles, but no right
triangles.
Does anyone know of a source for something like this?