Hi, I found this here on ifixit [post|647182|Sharp LC-50LB481U replaced bad LED's, still no backlight!-RESOLVED|new_window=true]
I also found this site that seems to be shipping out of the us, [link|https://www.shopjimmy.com/sharp-tt5008t-v1_00-v0_00-led-backlight-strips-12-lc-50lb481c-lc-50lb481u-new/|shopjimmy|new_window=true], otherwise there are plenty of eBay items.
Hope it is to any help.