Vendor availability of the 30mm stateside at the time of writing is poor outside of JW Winco/Ganter's direct sales site. You may instead opt for the 40mm (JW Winco/Ganter 6335.4-ST-40-M8-40) bolt which still fits and doesn't interfere with the components inside the deck:
Alternatively, you can get the 30mm stud in stainless, which while more expensive is at least the correct size: