Based on the installation manual it appears the case is made out of steel, and the PSU shroud appears to be integrated into the case. You may just be able to get some strong rare earth magnets (look for something thin) or else magnetic tape. It depends on the weight of the frame. I use both for different applications on my case.

https://www.amazon.com/s?k=rare+earth+magnets&crid=25MEDL6R7RKBW&sprefix=rare+%2Caps%2C68&ref=nb_sb_ss_ts-doa-p_1_5

https://www.amazon.com/Magnetic-Adhesive-Backing-whiteboards-Organization/dp/B07QKNZZ3J/ref=sr_1_7?crid=2JE6FNTROH2TZ&keywords=magnetic+strips&qid=1652231391&sprefix=magnetic+strips%2Caps%2C75&sr=8-7#

Good Luck.