The buttons cracked with age, the 5 speed buttons are rare compared to the 4 speed ones you find on eBay in the US, but even they are harder to find now. Nissan made some replacement ones years later but the wood texture and shape was slightly different to the original.
I managed to find a couple of 4 speed ones and just flip the buttons out for the 5 speeds I got off Taylor. Taylor can chime in if he likes, but I believe he was trying to improve the finish further before selling them. They have minor imperfections but I was happy with them still.
72 240z
70 240z
Details here.
http://www.viczcar.com/forum/index.php/topic,14508.msg154428.html#msg154428