Try Numrich Gun Parts Corporation
They have many schematics. Also, if you browse through their parts list of your H&R, they will tell you if it is for the .38 or other calibers.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)