Do you think ALL coco contains gnats? I've often wondered this?If you need a lot you're better off contacting a local agi wholesaler and getting that way. Only issues is if they allow you to set up an account, its usally farms oir if you have a reselling business. Hydroton will be hard to get bulk as there's always shortage of it around and usally can only get from hydro wholesalers I've never know any other agri wholesaler that carried hydroton.
For coco look for places that make custom soils they'll probaly have coco but be prepared for gnats as they'll have the coco sitting outside while their flush it over time to remove the salts.