There is only the one place to purchase Glide that I know of:
http://www.bobbincentral.com/
Glide is a 40wt 3-ply trilobal polyester thread. So Fine is a 50wt 3-ply polyester (not trilobal) thread. I have not tried So Fine. Tried King Tut cotton, Signature cotton, and Connecting Threads Esssential Pro polyester (70wt) in my longarm before trying Glide. All I use is Glide now because it is the only thread of the 4 I tried that never shreds or breaks on me while I am free motion quilting on the frame.
You may also want to try Sigma thread from
http://www.metroemb.com/store/ . It is on sale right now ($2.75 for a 5,000m spool), making it about 40% of the price of Glide. Quilters say it is very similar to Glide in both strengths and looks, although Sigma may be a little shinier. (Glide has a nice shine to it that I like for my quilts; adds a little sparkle.) Sigma is made in China whereas Glide is made in the U.S.
Here is a link to a recent thread about Glide and Sigma:
http://www.quiltingboard.com/main-f1...m-t232107.html