Spacer? No! You need 3mm of hardened steel washers to go between the knuckle and the caliper bracket to center the caliper and that's it.
2M5Z-2B120-AA List $173.35 CEG $130.01 Core $70
2M5Z-2B121-AA List $173.35 CEG $130.01 Core $70
2M5Z-1125-AA List $85.00 CEG $70.07 X 2 $140.14
W500443-S426 List $2.19 CEG $1.64 x 4 $6.56
This plus pads and brackets unless you want to do it the way
Rara did and grind a little off the back of one of the pads & retain the stock SVT brackets.
So if you don't need brackets about $340 total with pads & everything.