We do reports about famous Pennsylvanians in October. Later in the year, Rachel Carson comes up for her work with DDT and bald eagles. That student is always proud, like they did the science work, lol.

Philo Farnsworth, the boy who invented TV
Dr. Patricia Bath, inventor of a technique to remove cataracts
Nancy Grace Roman, the inventor of the Roman Space Telescope
Here is a few more
https://www.mentalfloss.com/article/638823/scientists-who-didnt-get-credit

I try to add diverse inventors to each unit which we read and write about. My firsties love learning about famous people that look like them. I hope to plant the seed they can do it too! I always start with Garrett Morgan who is from Kentucky like my students and myself.

These may not be lesser known nessecarily, but I think they are widly relevant and kids LOVE them.
Mark Rober is an engineer and as he would say "friend to science". I love that he makes science cool and relatable. Here is his instagram,
https://www.instagram.com/markrober/
Emily Calendrelli is known as the SpaceGal and is soon to be on the list of women that have been to space. I absolutely LOVE LOVE that she is a women that has been dreaming of going to space since she was in elementary school. She is the definition of if you can see her, you can be her!!! Here is her instagram,
https://www.instagram.com/thespacegal/

I'm not sure how much you can use on this, but I would do a mathematician of the month on a bulletin board (I know you said scientist, but it's a similar concept and many of them are scientists as well). Students loved being able to look up books in the library or on Epic, as well as watching the videos that I would link. (It's not editable because I couldn't upload something that was, but feel free to use this information!)