I found my cookbook!
Are you still looking?
I know there are lots of kidney recipes out there (Davita site is an education- they even have a roasted red pepper "tomato sauce" a bit like mine!), so I thought I'd just post what my book says about substituting for wheat flour- "for 6oz/1.25 cups of wheat flour, substitute 4oz/0.75 cup of cornmeal OR 5 oz/0.75 cup of rice flour.
And here is a gluten and dairy free white sauce, which you can flavour up whatever way you like:
2 level tbsp cornstarch
1 level tsp mustard powder
0.5 tsp lemon rind (not sure if this is too much for him?)
0.25 tsp nutmeg
1 bay leaf
black pepper
2 cups rice milk
In a pan, mix cornstarch, mustard and a little rice milk until smooth
Add remaining milk and all other ingredients
Bring to the boil, stirring constantly.
Simmer 2 minutes
Remove bayleaf
Use this as is, or add whatever herbs or vegetables he can have, and enjoys, to ring the changes. You could also substitute a stock for some of the milk to make a more velvety sauce.
HTH