I've been having difficulty finding a battery and battery charger for the handbuilt NES portable out of the book due to that the part number for Radioshack in Ben's book is obsolete. I found another thread discussing this, but that was from several years ago and that was obsolete also. So any help in suggesting a proper battery and battery charger would be great.

Well the for battery you can call up radioshack and ask if they have a 9.6 v battery and charger. Although its not a great battery but should do just fine.

Indeed, don't limit yourself by what is in the book. All you have to use is the proper voltage and make sure you have decent mAh. As long as you purchase the same male / female parts to hack the battery and the charger so they fit together, you wont have any problem if it is something different. When I started mine over a year ago, there wasn't the same part as well. But I was able to locate something very similar with lower mAh in a local Radio Shack.