How big did you want it to be? If you wanted it to be big(8feet by 8feet) you could use 2x4's and chicken wire(or something similar). 2x4's are like, $3 for an 8 foot piece, so to make an 8x8 pen would cost you $24 plus the wire, which shouldn't be all that much. However, ease of dissasembling isn't really an option there :/