The front bumper cover for the 996 1999-2001 will fir your Boxster, but will have a center opening for a central radiator.
Porsche offers factory Aerokits I & II (II is similar to the GT3 nose) that fit the Boxster but you’ll most likely want to add he side skirts that balance out the look.
AeroKit I
AeroKit II
There are also several aftermarket front bumper covers, usually made out of fiberglass, that are made for the Boxster.
Here are several examples.
http://e-partssales.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=P&Category_Code=986AK
Ruf makes one.
As does Techart.
If you google Boxster front bumper you’ll see lots of options. You can even add one that looks like a 987, 997, or a GT3 RS
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