Bone marrow (tuetano) in Houston

Does anyone know where I can buy uncooked cut bone marrow? Preferably length wise. Pucks aren't exactly what I'm looking for, but I'll take it if there isn't any other option.

I have not been able to find it anywhere, even the Mexican markets which I figured would have it.

Additionally, anyone know a good place to get some good cooked Mexican tuetado tacos?