Hello Barry.
Thanks for your post which I note that nobody has replied to yet, which does not surprise me because there are no easy answers to this problem.
I thought about it for a long time and tried all sorts of different things to find a solution. unfortunately, in order to provide the sort of support for a bag that will not result in leaks, the whole area around the stoma would need to be pressurised, leading to a situation where the output has nowhere to go other than push its way oiut under the seal.
The answer for me was to stick the bag onto a DIY platform that the stoma poked through, that could then be secured with a waistband(or two).
After much experimentation I found that the most efficient design of platform was a rectangular 4x2inch shaped piece of plastic skirting board with the suitable 35mm hole (the size of my stoma). The bag was attached to the outside of this platform and the platform was secured with two waistbands borrowed from Coloplast equipment. (although the subsequent replacements were supplied by my stoma nurses).
Having said that, I have been irrigating for some time now and have found that the reusable irrigation sleeves are better as overnight bags because they come with readymade support belts. I had to make minor adjustments so that I could attach two belts rather than one but they work perfectly well and resolve the problems of wafers not sticking properly because there are no wafers!
I'm still experimenting with this concept and because I do not have much output at night now I irrigate, I found that I can get away with the device that is pictured on my profile, catching a fart! ( it uses a top from a 5litre plastic container and a condom, but any kind of plastic bag would probably work.)
I also found that using a stoma collar helped to guide the output away from the area of skin around the stoma so that by the time it went into the 'bag' it was nowher near the wafer joint.
I should perhaps mention that I was looking for a support for my parastomal hernia as much as for the leakage problem but hey! if if works for both, then why not use it?
Sometimes we have to develop personal solutions to these problems ourselves because the items often need to be bespoke and there is not enough demand for the commercial companies to research and develop things to make a profit.
Best wishes
Bill