cheap, 80's or 90's or current generation Schwinn derailleur cruiser bike, should be about 100, 150 bucks on your nearest big city Craigs List.

left, old basket bike, served me well 10 years; right, NEW basket bike. I put Wald paperboy baskets on back, supersize Wald front baskets.

I used the bike on the left so much I actually wore out one Wald front basket on it, and eventually snapped the frame.