Thanks Ian, much appreciated. On their own they seem to be as rare as rocking horse manure and I don't want to pay for another set of filters. My friend was going to 3-D print me one but his machine has gone up in smoke and he say's he can't justify getting it fixed or buying another.
I've just been looking at the Intrepid website and their enlarging system is there. Click on Shop. Part of the kit is an under-the-lens filter holder. I can't see why they wouldn't sell you one of these by itself. Must be worth a look if you haven't found the Ilford one yet.
It's probably 3D printed.
David, I have the enlarger kit and overall I am very happy with it - apart from the filter holder - which is a joke. I have made my views clear to Intrepid but other than a thank you I have received no further communication.
As you will see from the attached photo the holder is supposed to clip onto the lens and be held by the pressure of the two elastic cords however it doesn't fit any of my 5x4 enlarger lenses lenses although it may fit across the front cell of say a 150mm taking lens. The filter gels are supposed to be slipped into the narrow slot you can just barely see in the front of the holder, I had trouble trying to get one in under white light - I didn't even attempt it under the safelight
In all honesty I can't imagine anyone will attempt to use this seriously so I'll carry on searching for an Ilford version.