Solution found. I contacted http://www.datsunrestore.com which initially reported that the bulbs could be found at any auto parts store like Autozone, Advace, Pep Boys, etc. However, when I had visited Advance Auto the day before I started this thread, they could not help me. I simply walked out of Advance with the stock replacement bulb info (Sylvania #97).
DatsunRestore then pointed me to http://www.MidnightMoose.com for the bulbs. This helped a lot in my search. I contacted someone at MidnightMoose and got the following info:
I was able to search online and found that, as far as fitment is concerned, the side marker lights accept the following bulbs: 67, 97, and 1155. Using this, I found this site: http://www.lightlens.com/coloredbulbs.htm which had the bulbs I wanted. The part numbers I purchased are LB67A and LB67R.
Thanks to DatsunRestore and Bill W. from MidnightMoose.com for their help. I hope this info helps for others wanting to do the same clear lens swap.