You can request his Individual Deceased Personnel File (IDPF) from this resource:
US Total Army Personnel Command Att: TAPC-PAO (FOIA) 200 Stovall Street Alexandria, VA 2232-0404 This says "Army" but they also hold Navy/Marine IDPF's for WWII. As well as giving them as much info as possible, such as name, rank, serial number, unit, etc, be sure to cite the Freedom of Information Act in your request.
I have not used this resource, but I have seen the following info listed online:
"Copies of Marine Corps death certificates may be obtained from:
Marine Corps Commandant Code M-HP-10 Headquarters Marine Corps 2 Navy Annex Washington DC 20380-1775 Phone 703-696-1177 Fax 703-696-2072 "
For someone that might remember him, you can try veterans groups, contacts for which were found listed online as follows:
Iwo Jima Survivors Assoc. Inc. P.O. Box 310516 Newington, CT 06131
5th Marine Division Mr. Robert Hansen 2727 Vista Umbrosa Newport BeachCA 92660-3554 (949) 644-4583