Ablaze from PBL has 555 color-changers that only do the smooth transitions, no flicker. I have a pair in my Congo.

Exactly. I thought I remember seeing 2 different types before, one fast flashing and one slow flashing. Looks like PBLife carries the slower flashing ones....

http://www.pinballlife.com/index.php?p=product&id=2262

Cointaker slow fade do what you want.

http://shop.cointaker.com/product.sc?productId=835&categoryId=60

Comes in flex or regular, 555 or 47

CT slow fades work perfect. I have a few in some choice spots.

I've got some coming in from cointaker and Noflix, so I'll post about which I like better after they arrive in the mail.

Noflix color changers arrived, and I must say these are of a much better quality than cointaker. Noflix's 555 wedge actually fits snugly into my machines fixtures, while cointaker's 555s fit loosely. It must be that German craftsmanship thing again

I specifically ordered the "slow" fading type from Noflix, which only slow-fade the colors. There are videos of them on youtube if you want to see the change rate. The main thing was these had the traditional bulb-shape diffuse cap on them, which I needed for my overhead ramps and one of my pop-bumpers that has a hole in the top for the bulb to stick through. Noflix also has "superflux" versions without the bulb cap, and those can be used for regular domed pop-bumpers.

The prototype LED I got from cointaker was a fast-fade changer with a flash sequence at the end of the fade cycle. I was informed those were not for sale at this point, and that they couldn't find any prototypes on hand of the kind I requested (a bulbed slow fader).

I bought both ablaze bayonet and wedge from pinball life. The bayonet flickers and the wedge at transitions.