I had this same dilemma , and solved it last week! This solution is totally improvised. I have the new Juki virtuoso, and it works beautifully with cones. So I pull out one of my super cheap mega spools....
http://www.thethreadexchange.com/miv...Category_Code=
...as in $1 a spool and 3000yds (30spools - $30- 3000yd)...that's cheap stuff.
At first I thought of putting a paper towel holder on the wall and pulling the thread off of that...but with a long arm, you travel 4 feet in either direction, so that wasn't going to work. I looked around....guess what worked beautifully???
I took a "multi-pants" hanger...a hanger with four bars that open up separately and set it atop my machine, and over the spools of the machine. Because it is such a big contraption, it set there very secure and stable. I used one of my $1 mega spools, and, voila, NO PROBLEMS!!!
...I was so happy, and proud of myself... plus the quilt looks good too!
Good luck!