Hair colour tips for Nanami Cosplay

As the title suggests, I am doing a Kento Nanami cosplay this weekend and am looking for temporary/budget friendly options to lighten my hair to match Nanami from JJK. I already have a relatively light dirty blonde colour, and just want to lift it a shade or two to match. I am looking at options like waxes/sprays for something costume ready/temporary, however have seen L'Oréal Paris Magic 'Retouch Root Spray' and wanted to know if anyone has had any luck? Worst case I am happy to do a box bleach and call it good if I have to.

All help appreciated! (Based in Aus)

https://imgur.com/a/Ewfo5Z6 (link for reference)