Check at your local hobby/model train shop. If your local shop doesn't carry the ride kits, they may be willing to order them for you. They can be found in the "circus" section of the "Walthers HO Scale Catalog". (Some of the rides are also available in N Scale).
To find a hobby shop near you or one that does mail order, you can go to the Walthers web site.
Many ride model kits can be found at:
Are your models for sale?
No. The amount of time & detail work put into the models, does not make for a cost-effective product.