Does anyone know where I can buy an off-road manual wheelchair that I can push through sand/gravel? All the manual chairs have those skinny tires that get stuck in anything and the knobby tire bikes are built for paraplegics that can use their hands. My husband cannot even drive his power chair so I need to push him along but would like to enjoy the outdoors with him. HELP! Can't afford the off-road power wheelchairs and my husband cannot drive them anyway.