Suzanne Guldimann has a number of books out with decent arrangements for lap harp.
I had the same problem when I switched to a 26 from 36 string for busking purposes - I ended up rearranging a lot of my favourites by simply leaving out or transposing notes I didn't have, and with that much piano experience you can likely do the same, but it might be a bit exhausting to do while also learning harp technique.
Harpsicle themselves publishes a number of simple songbooks meant to fit on their harps, but I find they aren't particularly pleasant arrangements.
I'm about to leave on a three week trip so I can't dig through my sheet music now, but if you are still looking by then, remind me and I'll look through my collection for the ones that I know work!
Also, bad news, most dedicated harp sheet music is just as expensive or more so than the Sylvia Woods ones, due to the smaller target market than piano. In fact I've found the SW books to be quite helpful because often they contain "easier" and "advanced" versions of the same pieces, and the "beginner" ones tend to be geared toward fitting on smaller harps.