The last official firmware for the 1300a was the 1.08, which you can find on this page: http://liggydee.cdfreaks.com/page/en/NEC-ND-1300A/
This is a very old drive now, and most modern disks are not going to be compatible with it. I have one in a backup machine, and the only disks I would use in it now are Taiyo Yuden 8x +R, though Verbatim 8x might also work. I know for certain that the TY 8x +R works well in this drive using the 1.08 firmware.
You can buy TY 8x media online if you are in the US. Rima.com and supermediastore.com both carry it, but only in 100ct cakeboxes.
You can buy a new drive for about $20, sometimes including shipping, from Newegg.com or Zipzoomfly or mwave.com, and I would strongly advise getting a newer one. This 7200 series NEC/Optiarc drive at mwave gets good press around here: http://www.mwave.com/mwave/viewspec.hmx?scriteria=AA73210
If you aren't in the US, we may be able to help you choose another drive that is available in your country.