I might have PM'd you awhile back with my PSN ID. The Peace Walker fight can be aggravating, and definitely goes on a few minutes too long. If you see me on PSN, hit me up and I'll see if I can give you a hand. If you do want to solo it, then here is what I brought with me:
" ...you wanna help me out with the Peace Walker battle? I quit playing and just played Chrono Cross on the PSP because I'm fucking bored shitless of dying. x.x "
Machine Gun (Any will do)
FIM-43 missile launcher
RPG-7 rocket launcher
As many healing items as you can carry
Basic technique, Open up with the RPG-7 while it's not moving at the start. Then use the FIM-43 lock on launcher as it moves around, always try and lock onto the pods, but if you can't just lock on and fire away. Use chaff grenades when you can, and quickly switch to strike marker and drop some damage on it. When it starts using its EMP shield thing, switch to the machine gun and just blast away until it stops. Use a supply marker when ever you start getting low on ammo, avoid waiting until you are empty. The most annoying attack I found was the charge move it does, running at you, When it starts to get ready to charge, move into the space between the buildings on the side. Rinse and repeat. It's a longish fight that requires patience, but it can be soloed, and once you know the attacks, it's just a matter of waiting it out. Just a bit too long, otherwise an interesting fight.