Hey! I found one! hahaha.
Fuse, Gould A30QS1000-128, 1000 amp, 300 VDC
edit: This one is a little more reasonable:
http://www.grainger.com/Grainger/FER...MUT-Fuse-6UVD4
EDIT AGAIN!: This one is even cheaper. 600v AC so good for 300v DC:
http://www.ebay.com/itm/GOULD-SHAWMU...-/350502626617
I just thought of another idea... 300 amps on the battery side is a lot for poor lead acid. There's an option in the controller to limit battery amps, which doesn't affect motor amps until the PWM duty gets too high. So you could still do burnouts at 1000 motor amps, but not blow the 300amp fuse, as long as it was on the battery pack B+ or B-.