Currently, we are testing several reed relays for high voltage. The photos of tested relays are included. 

Considered switches are

Reed Relays high volt reed relay A-NO 50W 3V 5VDC 
https://eu.mouser.com/ProductDetail/MEDER-electronic-Standex/HM05-1A69-08?qs=i5ZBw0Ef3zpYTgrC8SsmkA%3D%3D

Reed Relays 24VDC 50W 1 FORM A 
https://eu.mouser.com/ProductDetail/MEDER-electronic-Standex/H24-1A69?qs=k5V78Jg%2Feq4W2mMBAX%2FBSQ%3D%3D

RELAY REED SPST-NO 2A 5V 10kV
https://www.digikey.com/en/products/detail/sensata-cynergy3/DAT70515F-HR/5067361