Dear …
While sorting through various business cards I have collected over the last __(# months/years)__, I came across your card. You and I met at __(describe how you met)__ on __(date)__. I recall it was such a pleasure to meet you and I wanted to follow up with you as promised.
I remember the great discussion we had about __(briefly describe what your conversation was about)__. Though we didn’t have a lot of time to spend together, I thoroughly enjoyed our chat and was actually a bit disappointed that the time constraints didn’t allow for a longer conversation. Perhaps now, we can arrange for an opportunity to share some more thoughts on __(briefly describe what you had in common)__ .
If it fits into your schedule, I’d like to __(treat you to/get together with you for)__ lunch sometime between __(date)__ and __(date)__. If this works for you, please let me know so we can set something up.
I look forward to hearing from you soon.
Sincerely,