Before you search for the remaining elektros, you might want to know a few things. Firstly, there are 93 total elektros in the game, not 100. The achievement for all elektros also requires you to deposit them all back in the city power plant so remember to do that.

Secondly, this game has so many small nooks and crannies that are very easy to miss so when looking for the final elektros, enter any window you find and try to approach everything from new angles for a more complete view

This one requires you to get up on the hospital roof spinner thing. The elektro is easy to spot and if you aren't sure of where the hospital is, it's the building with a book on it, left of the post office

Due to the housing crisis, this elektro moved into the nook between these containers. There's an open door you can enter through and pick up the goober

This elektro is a big fan of birds and decided to become a crane operator. Go collect them before they get incredibly disappointed

I'm putting this one last because it requires that you've finished the game. After finishing the game, there's a hole that has opened up near the big tower in the city. Go in the hole and you'll find a mission that rewards you with one elektro.

Those are the ones I remembered being a pain in my rectum so I hope this will ease the pain for you when going for all achievements. If there are any further questions, ask away and I will do my best to come up with a good answer!