Apparently Kensight is the only option for the aftermarket Ellison sights, but they are available not only directly from Kensight, but other vendors too, for example, Elliason Champion Sight Trijicon Tritium insert - Night Sights with Rounded Blade
or Kensight Adjustable Rear Night Sight Elliason Cut Steel Black Rounded

They are advertised as tritium inserts on the Kensight website, so it's kinda strange that they ship a different product, not as advertised. Could it be that you ordered a wrong set by mistake?

 

When I reached out to good folks at Kensight they said their supplier had sent all black ones rather that the ones with Tritium. I had ordered correctly. They still show them on their site. I reached out to see if they got the correct ones recently, but have yet heard back.

I also just emailed Shooters Box to see if they have the ones I need. Thanks for pointing me that way...

 

Not sure if this is exactly what you are looking for:

Kensight - Elliason - Adjustable Fiber Optic Target Rear Sight, Fits Colt Gold Cup and most Accro Ap

Check out the deal on Kensight - Elliason - Adjustable Fiber Optic Target Rear Sight, Fits Colt Gold Cup and most Accro Ap at MSP - Mounting Solutions Plus

www.mountsplus.com

Kensight Adjustable 1911 Rear Night Sight Elliason Cut Steel Black

This Kensight Elliason-Style Rear Night Sight is Fully Adjustable for both windage and elevation, and is a faithful, modern-day recreation of the...

www.midwayusa.com

Kensight Elliason Trijicon Tritium Insert Night Sight w/ Rounded Blade w/ Free S&H

Kensight Elliason Trijicon Tritium Insert Night Sight w/ Rounded Blade ON SALE 860-391. Kensight Night Sights.

www.night-optics.com

Amazon.com : Kensight Elliason Adjustable Fiber-Optic Target Rear Sight, Black, 860-361 : Sports & Outdoors

Amazon.com : Kensight Elliason Adjustable Fiber-Optic Target Rear Sight, Black, 860-361 : Sports & Outdoors

www.amazon.com

 

I had a pistol with Ellison rear sight. I used a dremel tool with a ball cutter and cut a dent either side of the notch. Filled it with white paint then put a fiber optic sight in the front. Maybe not as good as Tritium sights but worked for my old eyes.