This is the official 26th Regiment logo. I receive a lot of requests for where to get battalion level patches - e.g., 1/26 patch, 2/26 patch, 3/26 patch. Fact is, no such thing exists - not officially, anyway.
Anything you may find out there, such as on Sgt. Grit's site is BOGUS, and was created recently (I even spoke with the woman who created a patch to cover all three battalions). The official regimental patch is the one you see here. In our regiment, battalion levels did not have patches, they only had Guideon flags (much like the platoon Guideon you saw in boot camp).

In Vietnam, some battalion level signs were made for HQ areas, but nothing was official (see photo below).

Proof of this can be seen in the 1968 photo below, taken on Okinawa. There you can see the official regimental logo of the 26th Regimental Landing Team of the 5th Marine Division.

Hope this clears things up for everyone.