This is probably a silly question but...

I'm lvl 32 now and I'm trying to find new Restoration spells. Restoration is at 49 (holy crap does it level slow) but I'm still finding the same spells from vendors that I had at level 15. I think Turn Undead is the most potent one I have, being that it turns level 13 undead to run away. What dictates when you find new spells? The only thing I can think of is to track down the mage that specializes in Restoration at the college in Winterhold and get them from her. Even then, I'm not convinced that would work. Any advice?

I have the exact same problem.

Looks like the only certain way is the College and the restoration teacher there. Everyone else stops selling Restoration spells past the apprentice level.

Check here: http://www.uesp.net/wiki/Skyrim:Restoration_Spells

Looks like Colette Marence is the only way to get it done. What a pain in the keister. I guess I can see a Paladin going to the Mage's College in Winterhold to study more about the school of Restoration since it is so integral to his life's mission.

Well in all honesty you probably use more magic then the Arch mage himself lol You just need their knowledge, you don't have to worry about breaking your paladins roleplay, it can easily fit in with those whacky mages.