Patience, that is what you need.
Started in 2012 with two great lots coming with original Intellivsion I and most of Intv II hardwares CIB in mint condition... and Congo Bongo was part of that lot but not shown in the pictures. Most of INTV games were there in mint CIB: Diner, Commando, Dig Dug, Thin Ice, Thunder Castle, all Atarisoft games. With $1400, i had nearly over 90 titles. The missing titles were mainly the remaining Intv series and a few Activision, Coleco or Parker Brothers games (Tut and Cobra...) here in there. I finally completed my original 125 CIB last year. The most difficult to find was the LF1 and LF2 in very good shape for which I was always loosing the bid until... last year! It took me 9 years! so, patience.