With fdisk you can change the number of bytes/sector for how fdisk reads the drive, but that doesn't actually change the bytes/sector of the drive as far as I know; I know that the bytes/sector number is not stored anywhere in the MBR (Master Boot Record), so I would assume that fdisk, syslinux, and other commands get that information from the device itself. In other words, I don't think you can change it. As a workaround though, you might try:
In the syslinux man page, it talks about using the "s" option when installing to a CD-ROM, which also uses 2048 bytes/sector. So you might give that a try and see if it works, and let me know how that goes.
sudo syslinux -sf /dev/sdb1