It is so surprising to know that such a wonderful crystal is not available in abundance online. Luckily it can be still found online. Always buy natural volcanic earth-grown alum crystal. Some of manufacturer’s use chemicals to produce Phitkari, never buy the one with chemicals as it is harmful to your skin.
First time I bought phitkari online on Amazon. It was more convenient and I could also see the reviews. It worked very well and lasted for about 2 years. You don’t have many choices.
Most of Indian grocery store sell phitkari. If you can’t find on the shelf then ask shop attendants. In most of Indian shops they tuck it away behind the counter as it’s not the item people buy everyday. Ask for Phitkari Crystal Block for Aftershave as they also sell it in powder and smaller pea size crystals as well. It’s lot cheaper than you can buy on Amazon.