a 4 lb lard bucket will hold enough soap to make a 2 # batch of soap in. it fits easily in a moderate size microwave for melting your oils in. just do not pick it up by the handle when moving it or pouring soap. it's not a pretty site if the handle should snap loose.
i have used buckets pre-made lotion bases have come in ( just remove the wire handle if you intend use the microwave for melting you oils ) the ones i use i can easliy get 65 oz. of oils in it along with all the extra goodies. but i don't use a stick blender either, i hand stir with a long handled whisk and or a spatula.
check places like goodwill and yard sales.
heck i have been known to ask for soaping supplies for my birthday, christmas. mother's day is coming up.