​Facebook closed groups for fabric & zips all of whom I have ordered from successfully. You have to request to join them:
 
Crackers fabric - https://www.facebook.com/groups/CrackersFabrics
 
Bag Kits & glitzy bits - an offshoot of Crackers Fabric https://www.facebook.com/groups/BagKitsandGlitzyBitz 
 
Tania Fabric - pre-orders for cork & quilting fabric plus zips & pulls https://www.facebook.com/groups/TaniaFabrics
also has a website but not as much on there and pre-orders are done through FB https://www.taniafabric.com
 
Bags of Difference - Bonkers Bags and bling hardware  also has a webpage with some items to order
https://www.facebook.com/groups/BagsofDifferenceBaghardware/?multi_permalinks=828740551057648&notif_id=1618336297049470&notif_t=group_highlights&ref=notif
 
Zipper Station for zips also on ebay we used a No3 zip but a No5 would also work; they tend to be used on bigger bags as they are stronger  https://www.zipperstation.co.uk 
 
Bag makers groups which are closed groups also to join
 
Amy Lynne group - https://www.facebook.com/groups/patternsbyamylynne 
Leanne Mosely https://www.facebook.com/groups/craftedbyleannepatternsgroup 
Spencer Ogg https://www.facebook.com/groups/spencerogg
They all have business facebook pages, but these are for their fans and have freebies, which can be downloaded from within the files sections.
 
Youtube videos
Amy Lynne Butler MEthod https://www.youtube.com/watch?v=RFQ9xdHmTYY
Amy Lynne easy peasy pouch https://www.youtube.com/watch?v=wfwNBQj8vV0