I used to carry a length of polyester cord with me. (Sailor. Learned my knots long ago.) Was at the far point of a solo near century on my very new Mooney near Salinas, CA (where I was to learn later was not very bicycle friendly country) when my Avocet seatpost broke a clamp bolt. Tied the seat in place and rode it home. (It was a little forward, low and tilted nose-down. Painful to near epic level. But it got me home in a place I was brand new to, knew nobody and lost except my list of streets and turns.)