This is a late exhibition report.
The author of Time for Lenses(レンズの時間), Mr. Suzuki, held a little exhibition at Popeye Camera a few months ago. On display were photographs taken by him with rare lenses (like the Zunow 50mm F1.1) and fun, mostly unknown stuff such as some modified-lenses.
There were also a couple of his favorite lenses on sale, most with pretty decent price tags.
Intrigued by compact rangefinder cameras, I was immediately gravitated towards a modified-Yashica COLOR-YASHINON DX 45mm F1.7 converted to the Fujifilm X-Mount. Although by no means is this lens hard to find on the internet for sale, it's definitely a rare sight in person.
Legend says that this lens, which was originally paired with the Yashica Electro 35 series of cameras, was designed and made by the guys over at Tomioka. Tomioka famously made many great Yashica lenses in the past, and was also credited in manufacturing the legendary Yashica ML 55mm F1.2 on the C/Y mount.
Mr. Suzuki, having done various interviews with optics manufacturers, later confirmed for me that this lens was indeed made by Tomioka.