You need old motherboard in PSP x))
If it has old MB, you can flash it by yourself without Pandora Battery & MMC, but only if it has FW 5.03 & lower.
If PSP has lower FW than 5.03, you can update it on 5.03, then you use ChickHEN, then XGenUpdater or something else :)
I flashed my PSP Fat by myself. I updated it on 5.03 then used ChickHEN then Recovery Flasher 1.60 for downgrade FW to (CFW) 5.00 M33-6 & last step of flashing was 5.50 GEN-D3.

Sry 4 my english ^^