I don't know of a machine that does not use a bobbin under the base plate. However, they do make Self Threading Machine needles...
https://www.independentliving.com/pr...SABEgJCAfD_BwE
I'm not sure how they work but someone may come along that can tell you. You can also buy self threading hand sewing needles which I know nothing about...
https://www.amazon.com/Singer-Self-T.../dp/B000YZAPXS
I would suggest using a neutral color of thread (same color for all projects) & get lots of bobbins & wind them up with that neutral thread. That way you don't have to constantly be stopping to refill a bobbin. Maybe a friend could wind your bobbins for you when you need.
Also, I would suggest starting with a small project like a table runner or small wall hanging so you can get the hang of all the steps in the quilting procedure.