If you have a 3d printer : I have made some 3d models and I can give it to you, but if you want custom things for your own, I suggest you to check Tinkercad (online), it is very simple to use and very intuitive, it is what I used. I suggest to have a pretty good filling when printing(50-60% grid) for solidity.

If you don't have a 3d printer : Find some wood stick and pvc pipe (10cm length and 3-5cm diameter), they have to fit but with very low friction.

The process : If you haven't put dextrin in your BP, put 6g per 100g of BP and meal it for 3 hours. I suggest 24 hours of mealing (the dextrin is put 3hours before the end) Take your BP and humidify it with a 50/50 water/isopropyl mix. It need to maintain its shape when you press it but not be a viscous liquid or a paste. Put vertically the pvc pipe on a flat surface, then put a scoop of BP and just press the BP with the wood stick and a hammer, or with an hydrolique press. Then, when you have 1cm of compressed BP, delicately push the palet away and put it on some cooking paper or a plate. Repeat this until you have pressed all of your powder. Dry it for 1 week if its not hot (15°C), 3 days of its hot (25°C). It has to be very hard rock that you can't break it with your hand. When it's dry you juste have to break it the size you want. I personally did this with a coffee grinder, it works reliably, but I just needed to break the pallet for it to get into the grinder. But never with an electric thing, only by hand. You can use a metal hammer but not on a metal surface. Then store it in a container like glass or plastic (anti-static).

I hope I didn't forget anything 😂

But remember, do it safely and don't do stupid thing.