Ask owners about growth and they almost always want more customers. Faster growth usually lies with existing customers who know you, trust you and already appear in your diary.
The familiar but underused relationship: sales succeed with existing customers in 60 to 70% of cases versus 5 to 20% for prospects. Research cited by McKinsey says effective cross-selling raises revenue around 20% and profit 30%. Approach it deliberately without pushy add-on selling.