Tightscrews work pretty well. Moving to M5 and having at least 20mm of tension screw in the lug pretty much eradicates de-tuning issues.I've been using TightScrews on my snare since February. I used to have all sorts of issues with my Musashi de-tuning. I'm now playing one of Andy's snares but I've had no issues with de-tuning whatsoever since I started using the TightScrews. I'm sure they'll wear eventually but after a year, they still work very well.
Have you tried contacting them directly? It was a few years ago when I bought mine but I think I bought them straight from Tightscrews.my problem is i want tightscrews but could only find one store in the uk selling them and that at a ridiculous price. might give the spring washer or locktite a go.