The Aputure Amaran AL-M9 looks good. It is a credit card size light, quite affordable and seems to have good light quality if we believe in published specs and reports. Check the link in this post: Suggested backlight sources for scanning film with DSLR - #134 by JYG
Regarding DIY: Have a look at this: Let's see your DSLR film scanning setup! - #48 by EricBB for inspiration.
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