I currently have on eBay a NOS GM taillight lens for a 1969 Chevelle, p/n 5961097. This is the left side (drivers side) lens. It is brand new, still in the original factory packaging, which has then been kept in a heavy plastic Ziploc bag ever since I have owned it, which is over 20 years now. Removed from the packaging only for the pictures. Perfect for your finely restored 69 Chevelle, when only original GM parts will do. I have the matching right side lens in equally perfect NOS condition in a separate auction that is running currently. Both of them are being offered with a $9.99 minimum bid and NO RESERVE.
Link to left side lens auction:
https://www.ebay.com/itm/266852771842