There are a lot of options out there. I'm partial to the OWA antennas (from W4RNL and others.)
Here is one family of designs:http://www.cebik.com/content/a10/vhf/2mowa1.html
The 6- and 7-element versions should work, even if you have to shorten it a bit. One advantage
of these designs is that they use a direct 50 ohm feed so you don't need the gamma match, and
performance is pretty consistent across the whole 2m band.
Another source of designs is DK7ZB: some have direct 50 ohm feed, but the 28 ohm versions have
better performance (and are fed using a pair of 75 ohm lines.)http://www.mydarc.de/dk7zb/
My favorite yagi designs for simplicity are WA5JVB's "Cheap Yagi" designs. I've built these for
several frequencies from 121.5 MHz to 732 MHz. They give good gain with direct coax feed.http://wa5vjb.com/references.html
Here is a set of high performance yagi designs from G0KSC:http://www.g0ksc.co.uk/
Look through and see what designs attract your attention as being easy to build and meeting your
performance needs. We can then adapt them for 3/8" elements if needed, and move the center
frequency around, shorten them to fit your boom, etc. While constant element spacing can give
you pretty close to maximum gain, the newer designs with variable spacing allow much better
control of F/B ratio, sidelobe levels, and feedpoint impedance.
One other thing we need to know, however, is the size and material you are using for a boom.
There is a correction factor that needs to be applied due to proximity to a conductive boom,
and it is different if the element is attached to the boom, above it, or passes though it without
making contact. Here is some further information on how element mounting affects length, as
well as some recommended construction notes:http://www.ifwtech.co.uk/g3sek/diy-yagi/index.htm
So IF you are using a non-conductive boom, most sets of dimensions can be simply converted
to 3/8" elements (and shifted in frequency if needed.) With a conductive boom we also need to
know the boom width and mounting method. You are looking at a short enough yagi that it
could be built using PVC pipe or fiberglass rod for the boom.
Let us know what designs you like and we can make tweaks on it for you.