first go to this
https://www.youtube.com/watch?v=SA65gtAFI_g to learn how to extract vpk
go to Steam\steamapps\workshop\content\220\3473768105
extract vpk and put the files extracted into the half life 2 folder(ep2, hl2, hl2complete and etc) not the main folder with all of the addons. should a file be missing https://www.youtube.com/watch?v=9tETC1_Xr_0 heres the original uploader in the comments.
for some reason the sandbox vgui does not include this so in order to save all of our sanity trying to find it, i did so you don't have to. should bin not include any dlls not that i know if they are needed download the backup mirror. :3
edit: you will need to download the backup but i do hope this makes it more accessable
sound files https://www.reddit.com/r/HalfLife/comments/e15qj4/need_all_halflife_2_sounds/