SEEKING SOME INNER SOLES

After some hard wearing and lightly padded inner soles for my bushwalking/running runners.
I have been using the 6mm thick ones that came with my Inov8 runners that are excellent, and a perfect blend of toughness and comfort-they last longer than the runners! Can't seem to find any anywhere for a reasonable price.
If I can get 400-500 kms that would be good-more even better. I cover a few ks per year so no matter how good they are if not durable they aren't going to work.
Not after anything too elaborate nor especially expensive ($10-$15 range max so I can try a few types), nor more than 6mm thick-this is the hard part as most are thicker.
Not after boot nor work boot type ones, nor memory foam but lightly spongy/dense/firmish and durable as possible please.
I'll be using them to both run and walk in my runners.
Should you have a link or know where I could find them that would be great also!
Ta for any suggestions.
G
I have been using the 6mm thick ones that came with my Inov8 runners that are excellent, and a perfect blend of toughness and comfort-they last longer than the runners! Can't seem to find any anywhere for a reasonable price.
If I can get 400-500 kms that would be good-more even better. I cover a few ks per year so no matter how good they are if not durable they aren't going to work.
Not after anything too elaborate nor especially expensive ($10-$15 range max so I can try a few types), nor more than 6mm thick-this is the hard part as most are thicker.
Not after boot nor work boot type ones, nor memory foam but lightly spongy/dense/firmish and durable as possible please.
I'll be using them to both run and walk in my runners.
Should you have a link or know where I could find them that would be great also!
Ta for any suggestions.
G