You can buy the calipers new from Apikol here:
http://www.apikol.com/index.php/products/porsche/porsche-boxster-caliper-set.html
You can also get them from ECS here:
Left:
https://www.ecstuning.com/b-genuine-porsche-parts/front-brake-caliper-black/98635142103/
Right:
https://www.ecstuning.com/b-genuine-porsche-parts/front-brake-caliper-black/98635142203/
Or you can buy a used set and refurbish them for much cheaper.
Part numbers: 986-351-421-03 and 986-351-422-03
Part number breakdown: "986"=model "351"=front "421"=left "422"=right
Make sure that you get the regular Boxster calipers, not the "S" ones if you want to use the stock GTI non-PP rotor size "312x25"
You'll need the following brackets:
http://www.apikol.com/index.php/pro...10/a3-vw-mkv-mkvi-boxster-brake-brackets.html
You'll need the following caliper bolts:
http://www.apikol.com/index.php/bolts-porsche-boxster-caliper-to-bracket-short.html
You'll need the following brake lines:
http://www.apikol.com/index.php/dot-approved-braided-ss-brake-lines-vw-1490.html
If refurbishing you'll need the following:
Cross-over lines:
Left:
https://www.ecstuning.com/b-genuine-porsche-parts/brake-caliper-connecting-line/99635296100/
Right:
https://www.ecstuning.com/b-genuine-porsche-parts/brake-caliper-connecting-line/99635296200/
Dust caps:
2 sets needed of each
36mm:
https://www.ecstuning.com/b-genuine-porsche-parts/brake-caliper-dust-cap-set/95135191700/
40mm:
https://www.ecstuning.com/b-genuine-porsche-parts/brake-caliper-dust-cap-set/95135191701/
Pad hardware kit:
https://www.ecstuning.com/b-genuine-porsche-parts/brake-pad-hardware-kit/99635295901/
Bleeder screws:
2 screws needed per caliper
regular:
https://www.ecstuning.com/b-genuine-porsche-parts/caliper-bleeder-screw-priced-per-pair/93035191900/
Other parts needed:
Pads:
Any pad for 986 calipers will work. There's plenty to choose from.
Rotors:
Any stock GTI non-PP size rotor will work. Dimensions are 312x25
Installation is fairly straightforward. Remove the stock calipers, carriers, rotors, dust shields, and brake lines. Then install the new rotors, brackets, brake lines, and calipers. You won't need the stock dust shields, as they won't fit.