There are several online tools to help pick domain names. Note that most are free, but at least one is paid, and there are probably more like that. Anyway, with the free ones, though, is the chance that they won't allow using all extensions.
Oh, by the way, if these domain finding tools won't work, you can always mess around with GoDaddy or NameCheap. Those websites will sometimes give you little hints when you search for domain names on them. Also, another advantage they have is the fact they will go thru most extensions. For instance, you could find the a good combo for .club or .xyz - in addition to ones for .com or .net.