On fs.com you can order fiber in custom lengths. An armored pre-terminated 350ft OS2 duplex cable costs $128: https://www.fs.com/products/20720.html Non-armored would be as cheap as $40: https://www.fs.com/products/50147.html?attribute=58053&id=17...
If you don't have a conduit, you can buy direct-burial cable. Two strands at 350 feet would be $590: https://www.lanshack.com/2-Strand-CustomLine-Corning-ALTOS-O... 6 strands at 350 feet would be $687: https://www.lanshack.com/6-Strand-CustomLine-Corning-ALTOS-O...
If you have some extra length, just coil it somewhere in the wall and don't bother splicing or re-terminating it. You can also use keystone jacks or couplers at both ends too so you have flexibility later without re-running it through the conduit.