If your needs really are *just the odd letter* then you would do well to dispose of the inkjet and get a laser. I do have an inkjet for photo printing but use my HP laser every day, with very few probs.
As you imply, ij printer heads dry up and then have to do endless grunting and groaning to get themselves wet again - sometimes they give up altogether and it's time to get out the alchemy kit.
But to answer your original question, I've never heard of a combo. Wouldn't buy one anyway, 'cos you could guarantee that the failure of one would b+gger up the other.