Most bowls will rinse all the way around the bowl.
Some of the Old American Standard had little rinse at the front,
And the Kohler Cimarron has little rinse at the back.
The Toto bowl rinse is even.
You would be safe with a Toto Drake, Toto Drake II, Toto Ultramax, American Standard Cadet 3
These should rinse fine for you.
Models with CEFIONTECT are even better.
My main baths have the double cyclone flush, Ultramax II and Drake II with CEFIONTECT.
From the bowls I've tried, the TOTO products with double cyclone and CEFIONTECT work well with the Ostomy.
I've used these people before for supplies
http://www.bestbuyostomy.com/
My Ostomy was removed on November 18th 2011
But I did have one for eighteen months, which allowed me to try many different styles of bowls. Some were horrible at rinsing. There were a few pressure assist bowls that took five flushes to clear it.
The Toto bowls were able to single flush it.
You need the elongated bowl, and I would get the higher bowl. The II series by TOTO have the high bowl, the CEFIONTECT finish and the Double Cyclone rinse. All good things for someone with an Ostomy.