
Luckily Piglet loves the u/d, so that's not a problem I have - just the cost of it! £20-odd for 5kg isn't cheap! Working from the information available from purine lists I've found a recipe that seems okay.
Take a cup of rice, add 1 cup of milk and 3 cups of water, and slowly bring it to the boil. Turn off the heat and let it cool. If not all the liquid's been absorbed by the time it's cooled, heat it up again, then let it cool. You should have a pretty solid 'pudding'. Break 3 or 4 eggs, whisk them together and stir them into the pudding, heating gently to help them set. I find this makes 4 portions, to which I can add a spoonful of cottage cheese, or a little white fish.
You might find that your dal will eat the u/d if it's mixed with this rice. Perhaps half a portion with half his ration of u/d?
Most importantly, make sure he drinks a lot. An extra pint of water a day is good - a bowl at lunchtime, with maybe a little milk added to make it more tempting, means a bladder full of nice dilute wee a couple of hours later, to keep the bladder flushed. Make sure he's not going to be left unattended for a few hours after his big drink, or you'll come home to a
very large puddle!

So far (touching all available wood) Piglet's been fine. We test his wee every 3 months for crystals, and check the pH more frequently, just to make sure he's not getting too acidic. Hopefully your dal will pick up soon.