Unfortunately both Yakima Racks and Thule Racks do not offer a car rack system for your 2001 Buick Park Avenue. However, as an excellent alternative I highly suggest you check out the Malone HandiRack inflatable roof rack system as a superb solution for carrying all kinds of items including a canoe or kayak, skis, snowboards, surfboards, luggage, furniture, you name it.
http://www.orsracksdirect.com/malone-handirack-inflatable-roof-rack-mpg452.html
Here's a good Malone HandiRack video to check out. very funny too.
http://www.orsracksdirect.com/malone-handirack-inflatable-car-rack-video-demo.html