I have never seen beef fat for sale in my area of Spain... southwest, lots of pigs. "Beef drippings" (carne de goteo, o simplemente grasa de ternera)) literally.

Neither have I seen sheep or lamb fat commercially produced and sold. I save my own lamb fat from cooking and use it it many dishes. Lamb is generally very fatty.

You could look for fatty cuts of beef at the butchers, or, better still, as the craze is for lean meat, butchers tend to trim off the fat and throw it away. A friendly butcher is what I would try if I was in your situation.

My situation is farm country, where most folks, including myself, kill their own animals.