I buy Dead Sea Salt crystals and rub it onto dry skin before showering - messy but effective. You could try a mix of olive oil and sugar mixed to a paste and rubbed over your feet as well - this works really well on your hands so it ought to work on tootsies too
If you google 'fine sand education' it will come up with loads of education catalogue sites that sell fine sand for children to play with. Can imagine you'd get quite a bit for your money and it would be the sort of texture you're after.
I use either sugar or ordinary cooking salt mixed with a little baby oil. Works a treat and leaves lovely smooth skin after rubbing in and then washing off.