Re: outside shower
The manufacturer of that brand probably has both lever and round handles, so replacing with the same manufacturer's handle should be a snap. If you don't know the brand, take a handle off and take it with you to a good hardware store or plumbing supplier - NOT a big box wearhouse - they will have sample stems available to provide you with either a replacement handle OR an adapter to fit the handle of your choice.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!