I would have your stairs refinished. This means scraping all the existing finish off, which is a very labor intensive proposition. The only other thing I can think of is to overlay the whole deal with a vinyl floor material. I have seen vinyl floors (one piece, not tiles) that is so close to looking like an oak strip floor that even I couldn't tell it wasn't real. I visited the friends house 3-4 times and commented on how nice the floor looked (they had a very large compass points inlay cut into the oak strip looking vinyl) and they told me it was vinyl. I had to get down on my hands and knees and touch it to be able to tell. With this stuff you could cut and glue it down yourself with the two part seam sealer glue and mastic for the risers. I would apply 1" x 1" oak nosings to the edge of the treads using epoxy and screws and leave it the 1/8" high so the vinyl could butt into it. If this is possible to do, it is cheap, will look good, won't cost you a week of scraping or having to tear up your whole staircase.