Most of the people that have them know what they are and will never let them go. Most of them never went away from MH, but with more and more people going back they are going to be even more impossible to find. Your best hope is to scour ebay every day and hope that a yard-saler or junker posts one.
Write a solid company like hamilton and tell them of your interest... if they get enough, they might just make a batch. I have asked them to consider doing a preorder and see if they can get enough pre-bought. This would be a good time for them to jump since the hobby is getting stronger as the economy is and more folks are figuring out that LED isn't going to answer their prayers.
Heck, even M80 are getting harder to find since AquaMedic got stupid and quit making them. Seems like they made these decisions years ago and are just now running out of stock... and now the hobby is shifting again...