I agree. The fact he was the only one carrying the Explorer MMIV has always indicated it was a private purchase (like the Gerbers were in real life).
The Scalemead survival knife (more readily available in the Explorer Nigh Raider branding) however, was carried by six different marines.
Attachment:
Knife compilation.jpg [ 506.35 KiB | Viewed 2385 times ]
With so many having one, it is safe to assume that the smaller boot knife was the "standard issue" knife.
Attachment:
nightRaiderknife cropped.jpg [ 62.74 KiB | Viewed 2385 times ]