some cultures use Jalepenios , rubbed across their lips.
the capsacin in the jalepenio will stimulate them to fill. perhaps PM serum on the lips would work too.
I had used some Drugstore type of lip inflator (it contained cinnamon oil). which will cause the lips to swell, and feel a little like they are burning. of course, it is only temporary.
there is a device that sucks your lips into it, drawing more blood flow to lips :lip suction device
I have one of those, it does work, just DONT over pump, it will bruise your lips! trust me.. been there done it.
I had tried the bee venom, for me it didn't work much, probably because my lips are as full as they are going to get
your body is like Lego's, with the right building blocks and imagination you can build anything!