Does anyone know a domain suggestion tool? For example, if the domain I would like to order is currently unavailable I would like this tool to suggest another one for the same extension?

domaintools have one. But they are not really good ones because they are creativeless.

dynadot.com has one.

Try. Go Daddy. Place your suggested domain in their checker. Then look and see if it is available. If it is not. Then they show others that are the same with a different extension or in a worse case it is all taken up. Good luck.