What are some types of pythons or boas that dont get very big?

It depends on what you call large. Male ball pythons average 3-5 feet, females 5-6. Male Hogg Island boas, which are a dwarf locality of the boa constrictor imperator, are usually 3-4 ft and females are 4-5. There many types of small boas and pythons, those are just a few.