I used to get it (99%) from a pharmacist friend, now retired. The last I got was via Amazon so I assume it's still available. I use so little, it seems to last forever for me.
Very curious. In Europe I can buy very easily 99% isopropyl alcohol intended for nails cleaning and it is quite cheap. I have a 500ml bottle right behind me.
A some others said, propylene glycol works great for this and preserves phenidone for a long time. Because of all the vaping these days you can find this stuff just about anywhere now.
I got my 99.9% isopropyl alcohol in a 4 pack of 500ml bottles at the Costco Pharmacy a couple of years ago. I am probably good for a while before I have to look for more.