Just buy a few bags of cheap black eyed beans from shop, put them in a cricket tub, or any other tub with a secure lid - just make some really small holes as they can climb.
Take some weevils and beans with eggs (tiny little dots sticking on the beans) from your culture and place into the new tub, put lid on and just leave it. They don't need water or any other food. In a few weeks you will have loads of weevils crawling around the tub.
I found it best to stagger the cultures a week at a time. The 3 tubs in the top right are bean weevil cultures and a bag of black eyed beans.
These guys are really easy as all they need are beans.