There is a guy who makes an adapter from our 5x110 bolt pattern to any other one you wish... they are made out of aluminium and take 1-2 weeks to make... but then all you do is you bolt those to your existing hubs... and then the new wheels on to the new adapter... The only problem then is the offset of the wheel.
There's more to aftermarket wheels than the lug pattern. There's the offset and hub size. I made a chart showing what GM wheels will fit the Catera. No adapters necessary. I included sites explaining what offset is and how to measure it. I'd post it here but the formats are different and I'm too lazy to do it all over again. You can find these wheels on ebay or the salvage yards.