GregAtkinson I'm going to buy some from 2-3 different sellers on eBay; presumably their stock is older. I'll keep you posted on that.
There are a few old, non-flickering ones on eBay. Here’s an eBay listing that has them for about $2 per bulb with shipping.
https://www.ebay.com/itm/155900291630
Here's a couple pictures showing the differences. the newer (bad) box is smaller; the older (good) box is larger.
I bought about 150 bulbs from various sellers that will hopefully last until my kids put me in a nursing home. It’s a large box, but still a very poignant reminder of my limited time on earth.