The helicopter was the Bell-47D, military designation H-13D.
There is a 1/35 kit of it by MRC/Academy.
It is agreat kt, but does not have specifically M*A*S*H decals, but actual US Army decals from the Korean war.
If you want decals from the show, Revell has a 1/35 H-13H, which is actually a Vietnam War version, not Korean War. This kit has the same fictional markings that were used on the TV show.
The Revell version has alater features such as the rounded skid supports and separate fuel tanks as opposed to straight skid supports and one large tank on the D model (among a few other, smaller differences throughout).