Component for switching 1000V - 100Amps condenser discharge pulse
What you should do to get the cheapest usable IGBT's, 
is to buy a frequency inverter and disassemble it. 

A frequency inverter is a device that powers electromotors. It creates three sinewaves build up of pulses. It operates with pulses up to 80 kHz, so a pulsewidth of 6 microsec should be no problem. 

Voltages up to 500V= and current RMS up to 1kA, depending on the model: large inverters can power 500kW electromotors. So if you are willing to get your hands dirty, you can save money on your IGBT's!

Don't worry if you can find one to meet your specs: your pulse is just a slow 10Hz, maximum power 200 kW, judging from your specifications.

Your final question: Is there an alternative for IGBT's ? 
For your application, there is no better alternative!