I have heard of only one model of machine that utilized and endless bobbin, and it is a very vintage sewing machine (not a longarm). It was designed so that a spool of thread was fed in from underneath, eliminating the need to wind bobbins. Apparently the design was no very successful, because it never caught on.
These days I think the most you can look for is a larger bobbin -- I forgot the name of it (L or M?). They hold more thread, thus need to be changed less frequently.