When i first started reading about witchcraft and paganism, i thought it would be cool to have a special, beautiful, movie-like grimorium, and then, i found out that i only needed to find what works best for me, so find what works for you!
I allways liked artcraft and things that i can make with my own hands, and it turns out that this is the way my magic flows better, so i decided to make my bos from zero.
I used the coptic stitch binding method, replaced the materials i don't have like the special binding needle (used a big sewing needle instead), the bone folder and others (I cannot find the tutorial that i used for this one, but you can definetly find tons of tutorials om youtube) Be creative! It turned out not expensive at all.
I used purple thread for the binding, and for the cover i used the hard cardboard that comes in the block of paper, painted it gold, and voilá! It is a little fragile, but i love it!
Then, you can enchant or consagrate, or protect. Do whatever feels right to you, and start writing! I have a mix of watercolour, pens ans other materials in my!
If you don't feeel confident enough to make yours from scratch, you can use a bullet journal, a regular notebook, an old book that you can use (you can glue new paper in the pages). Don't hold yourself. It doesn't have to be fancy, or good looking, or ancient. It only have to be yours!
A few pages of my BoS, that i am still writing. It is in portuguese, cause i'm from Brazil.