Last Buick Sport wagon I saw was in Maryland about 10 years ago. Not sure of year or interior but it was also white and a total rustbucket.
1969 was the last year for the Buick 'Vista' wagons. Oldsmobile kept building them through the end of that generation ('72), but Buick dropped them in favor of bringing back the full-sized Estate Wagon for the 1970 model year. Then, with the '71 clam shells, all the divisions except Cadillac had a large wagon. From '70 - '72, Buick still sold the non-Vista roofed Special/Skylark wagon on the regular wheelbase, calling IT the 'Sport Wagon'.