You can find these special sockets at tool stores. I have seen them at KMS Tools, Princeses Auto (they had the cheapest cost for a complete set), if you have LORDCO Auto Parts in your area, they may have it too. If these aren't sources local to you, call a Snap-On or MATCO tool distributor. They will have them too, but at a higher cost. (These other guys buy their stock out of China)
I highly recommend buying a complete set of these sockets, if you plan to keep your Volvo. These type of fastners are used exensively in the Volvo and you will need them if you expect to do most service work. Good luck!
Hope I have been helpful.
I live in Vancouver, and the U.S. border is very close. While on an errand to the U.S., I stopped at a U.S Postoffice and put TRACS/ABS module in the U.S. mail to Victor. Much less expensive than Canadia Post, eh!
/HenryC