Mole paste on the westside?
You can get pre-mixed mole paste at the Central Market downtown. It's tasty. Add some chicken broth to thin it out, bake it with some chicken, and you've got a yummy, low-effort mole.
Is there anyplace that sells similar on the westside?
There's a small grocery store on Pico between Barrington and Granville that sells a good Oaxacan black mole paste, to which I usually add a little cocoa powder and sugar. The name is something like La Chiquita Variedades, and they also have (maybe only sometimes?) the large bread rounds that are used to make tlayudas. It seems like Villa Tacos on Venice also has authentic mole paste, but I haven't been there for a while.
It's funny, I know what you're talking about and haven't seen it west of about Western Ave.
Two other places to check are Top Valu on Inglewood south of Culver, and El Sazon Oaxaqueno on Washington Place north of there. My go-to place may be too far east - Expresion Oaxaquena on Pico near Arlington; they sell bags of it. Mmm.
I can't remember if Monte Alban sells some of the paste, but I think that they do (as do the Guelaguetzas that I have been to).
I believe that most Mexican markets will carry some and know that for sure Palms Market (near Motor and Venice avenues) does, but cannot vouch for the quality.
Good luck and let us know what you find.