I would like one also. My searches found this product. It does what I really want, to be able to set a desired altitude.
I think for the cost it is more practical to go with a full GPS board. This one is one of the cheaper out there.
I looked at laser modules for another project. Looks like its fairly hard to do without going near $500. I had thought of using ground based lasers with just the sensor in the helicopter. That would take some serious time for me to figure out.
Many projects use sonic rangefinders. They seam limited to fairly low altitudes.