When finding cheap boots, do make sure of the followings: Cheap boots can be very uncomfortable. I bought these boots from Forever XXI once and oh man I couldn't even last an hour wearing those boots.
Boots are not relevantly cheap. So it is hard to find boots for $20.00 but I was lucky when I found my Chrome boots.
I bought my Chrome boots from Platos Closet for about $15.00 (the original was like $30.00 apparently). I don't know why the previous owner would sell the shoes since they are from an expensive company... So I guess you should try thrift stores since. I actually go their a lot to find anything I can use for my cosplay. (I found a blue vest there I used for Tsuna lul)
Chrome Dokuro [Katekyo Hitman REBORN!]
Rin [Togainu no Chi]
Lucina [Fire Emblem Awakening]