Are there even wholesalers on site? The folk at the stall I spent most time at (that wasn't a bar) - the pancake, coffee and fruit juice place at the Park - seemed to have brought their own stuff in, and occasionally talked about going off-site to get more.
So I'd guess that either there are no on-site wholesalers or it's not compulsory to use them - but your best bet may well be to go straight to the horse's mouth:
http://www.glastonburyfestivals.co.u...stival-office/
Good luck!