I don't know of any bolt on beds, but you can buy the 12" extensions and "add" them to your bed. There are a couple of pages that describe the process. My question to you is do you want to put in this kind of work for a lathe that you still can only put the tip end of a shaft through the headstock? If you PM me, I can probably give you a couple of better ideas. If this is still something you want to explore check out: