There are multiple ways to approach this question. You could take the trajectory parameters from this postflight document. It doesn't have a full set of orbital parameters for all the cases you are looking for, but it is some actual tracking data which would have been uplinked to the AGC.
Then, as you are familiar with Orbiter, you probably know about the project I am working on. I am one of the developers of NASSP, an addon for Orbiter that simulates the Apollo program and that has implemented the Virtual AGC. You can fly full missions with NASSP that are using the Virtual AGC. So that would give you several options, none of which will give you the exact trajectory or state vectors in the AGC from Apollo 15, but pretty close nevertheless:
- Fly Apollo 15 with NASSP yourself.
- Get someone (like me) to generate Virtual AGC core files (complete erasable memory dumps, not just the state vectors) for the specific points you want to have. These core files can be loaded in the standalone Virtual AGC application and will then give you the complete state of the AGC at the times you want. I have flown Apollo 15 in NASSP and so have some other people, so we wouldn't have to fly the whole mission again to do this, just load up some old save files and generate the core files.
- Get someone (like me) to do all of the things above, but just for the state vectors. State vectors alone won't get you all that far with the Virtual AGC though, there is a lot more to making it usable than that.
This goes a bit beyond a simple question/answer so you could make a post in our forum to discuss more details of what you want to achieve.
Here an example core file for the Virtual AGC, it's an Apollo 15 pre LOI file and has everything the CMC had loaded at that point. State vectors and many other things. This will be very close to the state of the CMC during the actual Apollo 15 mission.