The pictures put a big smile on my face! Those "scooters" are mighty sturdy to to be so old and support the weight of adults!!!
What is hard about this is that the word "scooter" has a different meaning now...than you are intending (A child's vehicle consisting of a long footboard between two small end wheels, controlled by an upright steering handle attached to the front wheel.).
Believe it or not, yours is usually still considered a tricycle - because of three wheels - thus tri-cycle. Even tho it does not have pedals. (Although growing up we thought of them as toddler scooters, foot scooters or more commonly known as a "trike" or "trike" scooter.)
There is a good site that has the most complete list I have seen of manufacturers of tricycles....they have a contact us section that you could possible send them the information. Generally people with sites like this are more than happy to help you find the information....or may be tickled to find out a new trike they have never seen before!
http://www.tricyclefetish.com/Best of luck to you!