The Melles Griot model 05-LPM-901-045 will operate most 6 to 8 inch long HeNe tubes or heads.
Specifications:

Input Voltage: 115/230 VAC ±10%, 50 to 400 Hz.
Output Voltage: 1450 to 2050 VDC.
Output Current: adjustable 4 to 5mA. preset at 4.5 mA.
Trigger Voltage: >10 KV
Input Leads: 12 inches, 22 AWG. Flying.
Output Leads: Alden high voltage connector
Dimensions: 4.3 x 3.0 x 1.2 inches (109 x 76 x 31 mm)
Mounting holes: 2.3 and 2.5 inch center spacing.

Features:

4 second Turn-on delay (defeat by cutting violet wire loop)
Alden high voltage output connector
RoHS compliant