🚀 go-pugleaf

The Hamamatsu Photomultiplier Tube catalog seems to show that most
classes of photocatode material used in their PMTs have significant UV
response. The 200K and 250M classes, in particular show wide
responses, from roughly 120nm to roughly 300nm.  The photocathode
material in both cases is Cs-Te and the window material in both cases
is synthetic silica.

Hamamatsu devotes one of their catalogs to non-PMT phototubes (a.k.a.,
"phototubes"!).  The R1187 phototube, with Cs-I photocathode and MgF2
window, shows the best short-end response, down to slightly below
120nm, though extending "redward" only to about 200nm.

As I remember, Hamamatsu responds with their catalogs quite quickly.
Also, college physics and astronomy departments are almost certain to
have them on hand.