Larry Hall has posted these instructions to build your own crosley icey ball.

I think a parabolic collector built in modules made from mylar from an emergency blanket would be least expensive way to go, couple this with a sintered ceramic backing (That has good thermal diffusion and conduction). You could even use sheet metal and use heat pipes coupled to the ground or better yet ground water, and use that as a thermosiphon to pump water through the HX that the dish is focused on. The hot side of the HX is coupled to heat pipes connected to the a flat plate which connects to the absorption system.

I think the first priority should be well drilling technology and water purification from solar collectors. Then solar operated pumps, then farming tools, then refrigeration.   Low Efficiency, open air simple stirling engines, which can be operated from solar thermal can pump water and can be made crudely unlike steam engines. Use the stirling engines to pump air and use a bubble pump to pump water.

Stirling engines of this type can be made using just thin sheet aluminum wood or cork for the shell, or even clay or glass, and leather for the diaphragm.

One could couple heat pipes to the groundwater flow to ensure a nice temp differential, and when the water is pumped to surface one could use the solar collector to boil the water and then condense and filter through zeolite and clay to remove heavy metals.

Then they have clean drinking water, and water for farming, once they have farming then the refrigeration becomes key.

Also if they have the well drilling excavation technology, then they can manufacture a cave and use the earth as thermal insulation making the ice last longer and therefore the goods in the cave last longer.