I use the pixel-junk monsters deluxe demo (12mb). I also have gameocracy one legend of robot (9mb). These games are non-transferable and you need a OFW PS3 paired with a CFW PSP to copy them to the vita. Or if you have a CFW PS3 you don't need the PSP.
"1). Download your content to the PS3.
2). Transfer it to the PSP.
3). Copy your license file from PSP to PC (/PSP/LICENSE/).
4). Find the PKG of your game from Sony's website.
5). Transfer the downloaded PKG to the PSV Packages folder on QCMA.
6). Create a package installer bubble on Ps Vita.
7). Enable VitaUpdateBlocker for 3.60 on PC and Ps vita (You can also disable WiFi/enter Airplaine mode if paranoid).
8). Enter IDU mode on the Ps Vita.
9). Install the PKG you transferred to PSV packages (step 5) using QCMA on PC, and PKG Installer on Ps Vita.
10). Exit IDU mode.
11). Copy License file (Step 3) to uxo:/pspemu/psp/license on the Ps Vita."
You can also follow this!
I hope I aided your quest for the smallest base games. Sony doesn't make it easy though.