Dear [Insert name of congressional staffer],

Thank you so much for meeting with our delegation on [Insert date of visit] We were grateful for the opportunity to speak with the office about our legislative concerns. [Insert detail of visit here. A story that was shared, a question that was asked, a staffer’s response, etc.]
The legislation we are advocating for is an excellent first step in addressing the issue of [Insert lobby topic here]. Would it be okay if we followed-up with you in two weeks to see what your member might be able to do?
As promised, I am attaching both our delegation list and the leave-behind put together by the Friends Committee on National Legislation.  
We look forward to hearing the congressperson’s response to our ask in the coming weeks. [This provides space for the staffer to ask follow-up questions.]
Thank you again!

Sincerely, 
[Name]
[Email address]
[City/State]

Here is a list of the group that was on the phone call with you. [List full names, emails and addresses below.]
Name, email, address
Name, email, address
Name, email, address