What year are you in school? (What is your time horizon for applying to college?)
I think that admissions officers are not necessarily looking for specific ECs related to mechanical (or other) engineering, but are looking for someone whose ECs reflect commitment in something. There is an old saying about a river being “a mile wide and an inch deep”; applied to ECs, it means lots of ECs without much investment of time or effort in any one of them. I think that admissions officers would prefer applicants who are involved in fewer activities but more in depth in those activities. For example, my son was accepted to several engineering programs (including ME) with a fewer number of ECs but ones that he participated in for multiple years: 5 years of being on the school’s robotics team, and 4 years of being on the school’s wrestling team. (These schools probably weren’t what you would consider as “top schools” but it wasn’t his lack of ECs that kept him out of those schools.)
Can you find ECs where you have the opportunity to display leadership? To show involvement on a continued basis? To show that you are passionate about something? To demonstrate that you are a hard worker/good employee?
Also, don’t obsess on getting into “a top college” for ME. Many universities have very good ME programs even if they don’t have the cachet of being “a top school” (whatever that means). Broaden your search to include more than just the “top schools”.