That's a shame, it is one of the few parts that they have in stock.
MKP parts (Metalised Polypropylene film) tend to be smaller that FKP (Polypropylene film and foil) but I'm not sure they are manufactured at that voltage rating. FKP have much higher pulse current rating, and capacitors of that voltage have limited applications. I don't see any MKP listed anyway.
The only thing that comes to mind is mounting the capacitors flat (vertically) on the metal front panel and using well insulated flying leads to connect to the PCB. This would help matching lead spacing too. Then you would only have to contend with the thickness of the capacitors, not the height.
Secure mounting would be a concern, as would insulation from the metal panel. You would probably want to interpose an insulating sheet. The question is, would double sided tape or epoxy adhesive be safe and acceptable. Clearly it would be safer to create some form of flat plate clamp, screwed to the internal panel.