This subject has probably been discussed, but I’m just not up to the search right now.
Most harp music published by independent harp publishers tries to plan for page turns by having less in the left hand.
Yeah, it’s not always possible, but there’s usually a spot near the turn that would only require memorizing a few measures.
For some pieces, like La Source, for example, there’s just no way, though. Sometimes you have to memorize or have a turner, unfortunately.
Another thing to do is practice page turns just like you practice the notes.
Make photostats of the whole piece, and paste a new booklet.
Thank you Mel and everyone for the great suggestions.
David Ice had what looks to me a pretty useful idea for this.