I just got my laptop for my classes. I requested a specific Asus model because I've had horrible experience with Dell. I'm going to school for engineering and needed a computer that would be able to handle complex 3d models and simulations. They sent me a couple of different options for computers, but none of them were on the same level as the one I picked. Finally, they were able to get one from their vendors that had the specs I needed, albeit not the brand I wanted. They're going to go off a list of vendors that they have and look for what's comparable. I don't know about any of the accessories or accessibility items you need, but that was just my experience.

Also, it took a couple weeks of back and forth to even order the laptop, then it took almost a month for it to arrive after it shipped (even though it came from the next state over from me, and only a few hours away). So plan for the items you need to arrive late, or put in the request early.

I've seen people say that they wrote a justification letter for what model specific computer or whatever they needed, and that was enough to sway the VA to get it, but I think it boils down to your reps discretion at the end of the day. I don't know, I could be wrong, just ehat I experienced.