I would use an old test machine and compile the kernel that I wanted, then stick in a formatted floppy and run:
makebootdisk
Thats were I would start-- I <knocking on wood> have never been in that unfortunate situation.
Good luck -- post back if you have success
I know there is a way to make an ISO from the packages in the slackware repository, though I dont know how. Maybe you could make your own cd with the right kernel in it.
Just some random thoughts....