Your next question is what is a nice Circus worth. Expect to pay around $500 from a collector if it’s mostly working. Retail I’d say they’ll ask $2,000 but it better be working 100% and very nice cosmetic condition.
Any specific 40 year old machine is hard to find. I’ll be at Texas Pinball Festival this weekend. If you PM me (or post here if you can’t send PMs yet) I’ll let you know if I see one.