anyone know where to buy valve shims?

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2007 Mazdaspeed6 Grand Touring
I got a bunch of work done to my head and now I need valve shims to adjust the valves, I don't want to order from mazda as they want an outstanding amount, I did notice napa had them but after I ordered I was told they were on back order, please let me know if you know of anywhere it will be greatly appreciated!
 
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