My world is approaching 11500 MC days old, and for the first 7000 or so I had three bases in Desert, Mesa and Ice Spikes biomes - which don't get rain or lightning strikes, so that probably contributed to me never seeing one. However my fourth base is at a roofed forest biome I levelled, near to an Ocean Monument I drained and turned into a farm.
I needed slime blocks for helping me with the monument clearance, so I set up a tower in a nearby swamp biome which I levelled so I could see the slimes easier. It was here during a storm I got my first charged creeper. I detonated him with a mob to collect the mob head (the only legit way in Survival to obtain Creeper/Zombie/Skeleton heads as a token to go in my base. After that whenever there was a storm I'd drop everything and race to the tower, and in the course of 15-20 more storms I got three more charged creepers. I have the whole set of heads now; one creeper is still out on the plain glass blocked in, awaiting use.
Back at my first base in the desert which I've been recently renovating, I built a villager trading hall but didn't get may zombie villagers as most of the zombies in deserts are husks. So again I levelled an area in an adjacent forest/forest hills biome and built a tower in the middle to watch out for zombie villagers. But during storms I also look our for charged creepers. About ten storms in I've had what looked like a charged creeper on a ridge inbetween some trees just outside the levelled area, around 100 blocks away, so I raced out to tag him but I couldn't access the ridge without mining up to it (and being attacked by other mobs as well at the same time) and by the time I got up there he'd despawned. Bit annoyed, so I've made the ridge more accessible and keep some ender pearls in the tower now.
So I've defo had four, pretty sure another one too. If you put yourself in a good set-up to find them during storms, your bound to increase your chances.
Below is a pic of the last one I got, who is currently waiting in his glass prison
Nice! I'll try what you do.