Contact them direct and ask. Maybe it wasn't popular. Another brand tried 15ml vials and they barely moved. It happens (see various forms of Coke which ended up as needing re-branding to 'coke original')
If you manually type in the product you're thinking of a couple of them still show up but in general the bulk is out of stock at the moment due to raw shortages but will be coming back in due time rest assured.
USP used to have a bulk section here https://us-pharmacies.to/product-category/bulk-offer/
They had 500ml and 1L jugs of Test, Deca, Mast etc and some other staples but in the current landscape with raws can't offer this currently.