Doubt you'd be able to find it. Most WWII rifles were retired. Some were rebuilt several times before that. Many of those that got retired got lend leased to other countries such as Greece, Italy, Korea, many South American countries, etc. those that were returner and those that got retired here have been sold off. Others have gone to the civilian marksmanship program, and sold off. Then many of those owners may have traded and sold them, handed them down, parted them out, etc.
So, there may not be a reasonable way to locate it. If you know the Serial number, you may be able to find another manufacturer that could duplicate the serial. As long as it wasn't made previously by the same manufacturer, or they could add his initials to the serial to personalize it and avoid a duplication.
Do you know what model rifle he was issued.