I have purchased a Stoma Guard belt from Stomaplex.com and have been wearing it for about 2 months now. I too had problems with my belt digging into my stoma.
This product is fantastic, comfortable to wear...I hardly notice I have it on. There is a cutout in the stoma cover so your bag can still work without any problems. I no longer have to worry about my stoma getting banged around, my tummy is flatter, and it gives me a boost of confidence.
Because I am concerned about perspiring when I go to Mexico next month, I have purchaed a second Stoma Guard belt from www.stomapex.com
This will allow me to change belts and wash the other if it becomes soiled.
The price is $172.00 US, and to me, worth every penny.