I'm looking for coffee seeds for urban cultivation. The goal is
ornamental, not crop production, so information about the taste isn't
very useful and names like "arabica" and "robusta" are a bit too
vague. I guess this is a request for coffee's equivalent to "heirloom
tomatoe" seeds.

For example: Where can I get my hands on coffea arabica mutants like
Purpurascens (which has purple leaves) and San Ramon (a dwarf)? A
Purpurascens x San Ramon would be ideal.

Recommendations for photo guides of coffee plants from around the
world would be a good start because they could allow me to focus my
search geographically or to certain brands. It's not hard to get green
beans from anywhere in the world, but it is hard to get a description
of the plants by brand name.

Your council is requested.