I guess you can't post links on this site - any ways the adaptor I was thinking about is:
For effective seal against pollution and contamination of wells from surface drainage. Many state health departments have adopted codes which require the sealing of water wells. Well is perfectly sealed by expanding the high quality of rubber packet, drawing together the top and bottom castings by tightening of belts.
SLIP TOP PLATE - PAINTED CAST IRON
FOR SUBMERSIBLE PUMPS
SINGLE HOLE & 1" DROP PIPE
WELL CAP 5-5/8" to 6-1/4"
1" PITTLESS ADAPTER FITS 4-1/2" TO 8" CASING ID FOR WELLS UP TO 600 FT. DEEP (soli8d brass body)
Would this do the trick? And could we instal ourselves?