There's no way to install Molecular Shell with Henkaku without a proper memory card on the OLED Vita. There's no workarounds, hacks, or fixes currently available. Your only option is to just buy a memory card. You can pick up a 4GB one for pretty cheap, like $10-$15 somewhere. And it's always a good idea to have an extra memory card around as well, in case something goes wrong with the SD2Vita.