Second the shoulder strap. This one wraps around the whole board.
SUP-NOW Paddleboard Carrier SUP... https://www.amazon.com/dp/B012YCDK44
Here’s another one if your board doesn’t have d rings on the side
SUP-NOW Paddleboard Carrier SUP Carrying Strap to Carry Paddleboard Paddle Board Accessories for Women and Men https://www.amazon.com/dp/B012YCDK44/ref=cm_sw_r_cp_api_glt_fabc_G344CM9W6D2KBRBF3Y6J