So you've got three options:

Easy - Craft in chemistry bench

Medium - Raid beaver dams(if you have a flyer it's in easy but unless you've got a really good ground tame it can have it's issues)

Hard - Beezelbufo in Swamp cave (get a good Beezelbufo about 100 LV and above I'd say also you wanna have gas mask so you don't die in cave)