There was supposed to be a hotfix to address this, somewhat, but I’m not seeing it live yet.
I have over 400 now, for now on my alts, I’m using this macro:
/run BuyMerchantItem(8)
/click StaticPopup1Button1
They don’t stack so have bag space, it makes it a tad quicker.
I cannot find the original posters for this, but I’m not taking credit, just passing it along.
Keep in mind if the update to the vendor goes live, you’ll have to adjust this part of the macro
/run BuyMerchantItem(8)
Changing the (8) to the corresponding slot on the vendor.
Found them: