I just replaced both gaskets yesterday (the bottom gasket was hard as plastic) and I believe you can cut the upper one down to make a temporary bottom one. They appear to be the same thickness, although the upper one has a groove that the bottom one doesn't.

You'll have to be careful that the split gasket doesn't carry past the stop in the U tube when you push it on the turbo. BTW, the $9 gasket is the bottom one. The top one is around $4.

On a side note, the new top gasket was a real PITA to reinstall on the air cleaner fitting. I had to take the cleaner assembly off and try different ways (gasket in U tube, gasket on air cleaner, gasket seated, gasket partially seated) by pushing the U tube with the air cleaner assembly braced against a post. Finally got it, but I guess I'll be leaving the top clamped on and loosen the bottom one when I take the air cleaner off from now on.

What have you guys found to be the best procedure for reassembling the top gasket?