Device/circuit for high current, short pulse discharge?

I'm tasked with replacing a relay with a semiconductor switch in a high voltage, high current, short pulse duration application (all relative, I concede). Basically I'm charging a capacitor up to ~1kV and dumping it through a low-impedance load. The di/dt requirements are pretty gnarly: ~400A with a ~300ns pulse width. Due to other constraints it has to be a high-side switch, too.

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I originally tried using a high-power SCR, but all viable devices I've found have a di/dt limit of 100~150A/us, whereas I'm in need of about 2500A/us.

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My next plan of attack is using an IGBT with a gate-drive transformer, though I'll have to make sure to keep the leakage inductance low.

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My question, though, is if anyone has another approach to consider? The isolation is a bit of a PITA but that's the route I'll take if it's the most practical.

EDIT: we were using these voltage-controlled solidtrons which worked perfectly (in a 5-lead TO-247-ish package) but now this is no longer an option.