Flying Objects make a 9' travel cover in both 30" and 33" widths, great quality product and designed locally (in WA).
Most covers have a little bit of flexibility in fit, but will depend on the thickness and rail profile of your board.
If you want a tight fit, and not sure about whether it will fit the 30" version, maybe you could measure the circumference at the widest part of the board, divide it by 2, and check the internal width of the cover to see if it will squeeze in. (Thinking that someone on here may have a 9' x 30" cover to measure the width between the side seams to help you out).
www.flyingobjects.com.au/products/surf-sup/travel-cover-sup/ Available through your local Starboard dealer.