When I did more active development of my iOS apps I was always on the lookout for good icons of this sort. Sometimes I would even do my own using a tool called

When I did more active development of my iOS apps I was always on the lookout for good icons of this sort. Sometimes I would even do my own using a tool called ArtText2 from the image components they provided. I even sent them an email offering money for more components to build the icons from, which they never followed up on.