I rather like the Neutra Architectural Numbers available from DWR. But at $68.00 a pop, it could get pretty expensive. And they only do numbers. I found a company that does numbers and letters (that look remarkably like Neutra’s) for 60% less. The numbers can be installed flush or with spacers. They also do custom fonts. Lifetime warranty.
style shown: Deep Ribbon (left)
Neutra House Numbers (right)