Of course you can. It happens all the time. There is nothing stopping you from calling your Congresspersons office and asking for a meeting. Obviously the more people you represent, the better, but you’d be surprised how effective even a small group can be in terms of pushing issues.

Here is an example of a state bleeding disorders non-profit that meet with Senators in DC every year.

https://cthemophilia.org/events/washington-days-2020/

I also worked with an entrepreneurship group at a college. The head told a story where he went to DC and his senator had their staff type up the law with him there. Brought it to the floor that day. It didn’t pass but I was amazed at what got done through one person’s advocacy.