If you’re looking to experiment with just a small amount before deciding it’s worth purchasing in bulk, I’ve been able to find small packets of telephone brand agar at most Asian grocers for about $1-2.

Just buy a couple packs on amazon

https://www.amazon.com/Telephone-Brand-Agar-Powder-g-x2/dp/B00T1CWR7C

Use 2% agar. Meaning 2 grams per 100ml of agar you want to make. This stuff works well.