The cablestogo link appear to use in-line, not right-angle connectors (at least as near as I can tell). I did find a source that offers a 10 foot version using right-angle connectors, but nothing 20 feet long.
There are quite a few sources that offer custom cables, like www.markertek.com
Hmmm,
You are looking for what is called a balanced patch cable. Most of those have straight plugs, not right angle plugs or one straight and one right angle. The one Tee Time linked above also has straight plugs.
I did find one here for you. You might want to try a local guitar shop to see if they have one like it first.
Most guitar shops carry HOSA cables, but Hosa only has them up to 10 feet Model CSR-110R. HOsa does make the PLG-025SR adapter that will convert a straight 1/4" TRS to a right angle 1/4" TRS. You can see if a guitar shop has those or use the model number to do a Google search.
Thanks for all the replies. I did locate a 25' HOSA cable from Sweetwater and they also have the right-angle adapters. Looks like that's the cheapest way to go.