You wouldn't think they would be hard to find. I looked at Walmart, Dollar tree not to mention 3 other dollar stores and still could not find them. I have heard you could order them from ebay, but the shipping would not be worth it for me for a $1 toy!
I think you can buy them on line if you can do a search for the right name. Also people mention gettin ghtem at there local doller tree , doller store, I havent seen any at mine yet but Ill keep looking. I did see one sight that had them but they were like 5 bucks plus shipping
as far as i know you can buy one at the dollar store or make it. mine is a egg that i broke a little whole in the top and used a needleless syringe to suck out the egg. then i filled it with aloe gel and put my temp sensor in. then i seeled the top with hot glue and there ya go. i hope i helped
If you will search for water wiggler on the forum search box, you can get more info. It's a water filled cheap toy that you can stick a probe in to get an idea what the temp inside an incubating egg is likley to be.
I had a really hard time finding mine, I was just looking in the wrong places, my DW suggested one of the gazillion dollar stores. I found them at the first one I went to, In many sizes & colors to boot. I would not think of paying more than a dollar for them.