If you are handy, you can make some of those things.
Try the hupertufa forum and garden junk forum, and somone will probley tell you how. In the Hypertufa forum gallery under the title 'piglet' someone mentions the 'winged ball in Harry Potter. Also you can google for "Wylee's World" and see her grots.....Very interesting. The first page for Wylee shows her cat things--just scroll down and click on wylee's world and you will see amazing things. Sorry I can't do links!

I have a thing with frogs and gargoyles. It takes time and patience to find the right ones within budget. I've had fair luck finding them on eBay that were reasonable. Most people don't put a lot of time into the garden so there isn't much competition. Another idea is to check hobby/craft stores. They often have unfinished ceramics reasonable; and some have contacts with local artists.