The Domus Kits, which publish individual architectural structures from Greek
and Roman civilizations intended for people to construct, may be
inexpensive (relatively) solutions to your dilemna. The finished
3-dimensional model is generally around one foot tall and varies in length.
These kits are distributed by Silver Visions Publishing Co., Inc. and are
printed in Italy. Made from high grade heavy cardstock, they are not
necessarily for children to put together (pretty involved even with an
adult's help). Hope this helps!
Susan Reed
Indiana University Art Museum
Ancient Art