Irish moss is a flowering perennial, not a true moss and can be purchased in garden centres. It takes sun just fine. Unless you own the land with the hills, it is illegal, unethical to remove moss. Likely it wouldn't survive scraping anyway.

Do you want Irish moss or true moss between the stones? True moss needs shade and moisture and will tolerate very little foot traffic; Irish moss takes sun, dry conditions and will tolerant moderate foot traffic. It is marketed along with various thymes and other small groundcovers as "Steppables" -- plants specifically selected for use between stepping stones. You would likely be better off with those plants. At this time of the year they can often be picked up half price at garden centres.

Here is a link that might be useful: Stepables

I lost my Irish moss to the drought though.