I know very little about the Super K or Super O track systems, but RR-Track has 042 curves in the K Line Super Snap track library. Also, FWIW, it has quite a few other curve sizes, 030 (22.5 & 45 Deg), 042 (15 & 30 deg) and 054, 063, 072, 081, 096 & 0120 all 22.5 deg only. You might take a look at their website and see what you think, look around carefully at the base packages and track and accessory libraries.
The bad part about RR-Track is there is no trial version and not all track libraries are included. They have different packages, but as I recall, I don't think any one package includes ALL the track libraries. They have accessory libraries too, but it can get pricey if you start adding a bunch of libraries to your original package.
I bought it several years ago and have added quite a few libraries over time so hey are in to me for quite a bit. But, they probably have the most complete set of track and accessory libraries and pre-made sample track plans using a few different track systems like Fastrack, Atlas O, etc.. The track plans are also additional cost. I think they are grouped by track type as I recall.
There is also a learning curve if you want to use all of it's features. I have seen some pretty impressive plans, drawn by others here, using the full set of it's features.
