Are there any blood pack vendors other than Vandal?
According to wiki there are no other vendors for this item.
However, you can obtain The Odious Chalice which serves as refillable blood pack.
While there are indeed no other vendors who would sell you blood, at least in Unofficial Patch Plus you can use Dominate and Presence to make him sell you blood even if he dislikes you.
You can do a quest "Replanting a Lily" so he will work with you again.
Odious Chalice is a good thingie, but it is always better not to substitute Blood Packs with it, but rather have both.