Does it look bad to get recommendation letters all from the outside of undergrad school?
I would recommend getting a letter from someone in the field even if they do not know you personally, but this is based off of my experience from getting letters and may vary slightly from what you are doing. The guidelines I was given were to obtain letters from 1) someone who is able to speak to my academic talent and 2) someone who knows about the program you are applying to. In this instance, it would be helpful to get a letter from a professor where you did well in their class. If you need letters for other purposes (like a character reference), then it may be helpful to consider getting a letter from someone who knows you personally. If you get a letter from someone who has never gone to grad school, it may be difficult for them to explain why you would be a good candidate for the program you are applying to.

Even though you did not spend a lot of time getting to know your professors, you would be surprised at how many may remember you. I faced a similar dilemma when obtaining my letters, but it turned out really well. I recommend 1) emailing your professors with your name, semester you took them, and your GPA in that class and scheduling an in-person appointment and 2) bringing any application materials (like a statement of purpose) that may help the professor in writing you a strong letter. The worst thing that can happen is the professor declining to write a letter, and in that case, you would have the backup of asking someone who knows you better and is more likely to say yes to writing a letter.