His IDPF, also called 293 File, will give you all the info you seek and enough to locate and access other sources. You'll find the address and general instructions at message #2112 (enter "2112" in the box labeled "Jump to" in the top right corner of the main page, then click on "Go").
You can disregard a lot of the instructions given. All you need provide is his (1) name (first,middle initial and last) and date of birth. Any other info may be helpful but not really necessary. There's no charge but you can expect a wait of up to eight months; no way to avoid it.
You might also contact the DVA Regional Office nearest you. You can call but they'll only inform you that they require a signed, written request. Ask to examine his SGIF folder. It'll take a while but it's usually worth it.