They still make them, I believe Sally Hansen makes them, I saw them. I am trying to remember if the last time I saw them was at CVS, or Target. I was shopping for nail supplies at both places recently, so I'm not sure where I was when I saw them... But check both of those locations for the pencils.
Also if you have yellowing from nail polish, Sally Beauty sells a product called Bubble White, it is a soak for your nails and it removes stains. My MIL uses this all the time.
Also the last time I was at Sallys I bought something called ASP Whitening Nail Paste and it comes with a little scrub brush. I bought it for my toes, because after I wear red or dark polish on my toes and I remove the polish my nails are discolored. If I scrub my nails with the paste and rinse it off, it removes the staining. If they are very discolored I leave the paste on longer. This allows me to wear a clear polish for a natural look on my toes if I want to.