They're the only game in town for new axial HV caps as far as I know. Otherwise, you need to order directly from a parts distributor. We're lucky anyone sells them in small quantities.
Surplus Sales of Nebraska has some old axial Sprague caps that could also be used. The value is a bit larger at 0.015uF and they're a few decades old but should work.
$4.25 each if you get 10
https://www.surplussales.com/items/1...age-capacitor/