I want to add pictures via "other" site's url(ex;imgur) to media library.

Hi.
I’m in trouble with my wordpress site.
It has very many pictures, so it takes a lot of traffic.
I can use ‘Add from URL’ option, but it can’t be uploaded to portfolio
-because to upload in portfolio, it needs to be uploaded in media library first-

in my country, ‘taking a lot of traffic’ means ‘taking a lot of money’.
and I have sub-blog that is free. (so i can copy URLs of my images in sub-blog to my site)

so i’m using a plug-in called ‘Google drive WP media’, and it helped me to decrease the amount of traffic used.
But It takes so many times to load all my pics bcz Google drive’s so slow (than my sub-blog)
And my site is accessed by china too, but china can’t access google so they can’t see my site.

in conclusion,
is there any plug-in that can upload pictures to media library via other site? (ex; imgur, ImageShack, TinyPic, StoreMyPic, tistory or sina image, something…)
except google drive.
I mean, it must activate like ‘google drive wp media’ but it dose not use google engine.

I know it’s difficult,
but I want your help keenly.
I don’t matter it’s free or charged.

I wait for your reply.
Thanks, and sorry for bad english.