Is there any way if I have my +1 be xanathar and get the cantrip booming blade? .....
Find an adventure or earn a certification that allows you to learn the cantrip, if said adventure/certification exists......
Or find Fai Chen at a con and get a good trade. I don't know if Fai Chen has cantrips for sell or trade. Fai Chen is con activity which allows you to trade magic items/gp for stuff.