Listed below are the most frequently found locations to acquire fenbendazole.

Retail

Fenbendazole may be obtained at a bigger retail store such as Walmart or Costco.
You can also find it Veterinary pharmacies and pet shops.
Agricultural supply stores, where Fenbendazole can be found as a dewormer for livestock.

Online

Amazon

Fenbendazole is readily available on Amazon, where various sellers offer high-quality products at competitive prices. Furthermore, purchasing on Amazon is secure and dependable.
Amazon site Fenbendazole

Direct from supplier

Fenben lab
Just fenbendazole powder or capsules with no fillers. Great quality. The brand offers free shipping worldwide.
Fenben Lab site

Sigma-Aldrich
One of the biggest chemical product manufacturers in the world. The company offers analytical standard quality, fit for research. They do sell it on their website, but purchasing it is not easy:
Sigma-aldrich site

HomeLab Vet
The brand has many fenbendazole options, powder, capsules, tablets, liquid solution. HomeLab Vet is located in Ukraine.
HomeLab Vet site

Panacur / Safeguard
Most popular Fenbendazole dog dewormer veterinary brands in the world. Both brands are made by Merck. Panacur and Safeguard both have product versions designed for house pets and farm setting.
Since Merck does not sell directly to consumer their product can be only purchased though 3rd party sellers on Amazon or eBay:
Panacur / Safeguard on Amazon