The on-time charging of Renewable Sensor Nodes (RSNs) prolongs the lifetime of the Wireless Rechargeable Sensor Network (WRSN). However, it necessitates the prompt and accurate transmission of Charging Requests (CR) from RSNs to Mobile Charging Drones (MCD), and accordingly the charging trip is planned by MCD. Most of the existing algorithms attempted to forecast the shortest path, which may not be an optimal path for the current network traffic. This causes increased packet loss, retransmissions thus consuming more energy. To address this, Firefly-based Optimal Path Selection Algorithm (FOPSA) is proposed to find an optimum and stable path for the on-time delivery of CRs to MCD using firefly optimization. The proposed fitness function utilizes geometric mean of the residual energy, distance, and hop count to predict the routing path for the transmission of CRs. It ensures that the path has potential RSNs with adequate energy to avoid routing holes. The proposed algorithm is simulated and compared with the existing algorithms in terms of throughput, packet loss, residual energy, and delay.