I love brewing kolsch even spring. Before I built my fermentation chamber I would watch the weather and brew when we had a string of 50°-60° days and put the bucket on the porch. I used a highly rated beer smith recipe that was 75% German pilsner, 20% Vienna and 5% carapils. Hallertuer hops (60 and 20. min) and LalBrew Koln Kolsch dry yeast. While I cannot speak on the final product being worthy of comparison with the real deal, I really enjoyed these, especially as a change of pace from all those hopped up ales I would brew. I recall my neighbors had tapped a keg of Coors Light and so I filled a growler of my Holsch and brought over some for them to taste. While I have often seen them with limit pushing hoppy craft ales before, I thought a good opportunity to let them compare what is possible versus the coors keg. They loved it, like ravingly surprised as they discovered how good beer can be when malt is the star.
It's too bad you never see Kolsch on shelves unless you go to a distributor so that you can pick up some on an impulse buy. IMO it's too good a style to limit to a seasonal thing - I guess it just doesn't have the wow factor in the fight for shelf space.
I didn't catch if you mentioned which maltster's pils you've tried, but certainly stick with something European and they are plenty available in the states.
Weyermann Barke
Avangard
Best Malz
Ireks
Some Kolsch recipes will have some low additions (5%) of Vienna or a touch of Melanoidin to simulate a decoction mash. No problem with doing that for some extra interest.