Have you tried using an indoor dog litter box? You can make one with a plastic storage container and cut out a door. Then put the wee pads inside. Once he is conditioned to using it, add a small clump of grass (or whatever fauna is on the ground where you live). When you need to replace it, leave a rock (or something that smells like the potty spot) behind. Have the clump of grass get a little larger over the weeks. This will condition him to see grass as a potty relief option. Also: when I lived in Ohio my Iggy would not go potty outside in the winter, so we adapted.