I'm reading this from the UK & I am a small 36. Some brands/models run small. In a couple of my shoes I take a 37 (which I have never taken in any other shoe). So therefore, someone taking a 35 should find that some size 36 MIGHT fit. I think Specialized run true to size whilst Shimano vary a lot depending on model - my carbon soled Shimanos are size 37. Keen cycling sandals in a 36 are pretty small. Also i got rid of some Pearl Izumi that were too small in a 36. It's a really bad idea to buy shoes that are too big (either because you can't find a smaller size, or because you need the width) - it makes it very difficult to get the cleats in the right place.
Sidis are probably also worth a try. If the person is in the UK, I would Google the Cycle Promotions sales - they have a range of odd sizes, often very small.
I find it almost impossibly to buy trail running shoes & many other types in the UK as most brands start at a 4/37. Some people have told me that you feet get bigger (spread?) with age - I do hope so!