Zenith ch 17Z22Q nonpolar cap issue

[ha1156w]

I am finally a couple of years on catching up on projects set aside. In this case it's my Zenith 17Z22Q chassis 21" B/W tabletop. I've recapped the chassis and ran across a strange one - There's a nonpolar cap 10uf 400V (C3 in the Sam's) strapped to the chassis right next to the HOT socket. It appears that sometime in the stone age it arced between the cap and the HOT socket, through the plastic "ring" Around the socket on the underside. Cap has a hole burned in it at about the 4 o'clock position close to the chassis, hidden from view until removal. What would have caused it in the first place? I assume they knew what they were doing when they riveted that cap so closely to the tube socket. Factory goof?

I've had a bit of trouble sourcing a bipolar cap in that voltage. Anyone I can pick at? My usual vendors aren't stocking anything that high, not Mouser, not DigiSneeze, etc. Who has something to replace it?