You can't, at least not as Hynix modules. But many different sellers rebrand Hynix for resale (like Apple does...)
BUT:
There's absolutely no reason to match brand for brand/chip for chip when upgrading memory*
Just choose a reputable seller who tests and guarantees compatibility with your model Mac, offers a lifetime warranty and a no-cost return if it doesn't work.
Thanks
Trevor
CanadaRAM.com
* OK OK There is one reason -- if you have a first generation iMac G5, and you are obsessed with getting "128-bit" access (which apparently has little or no real world result) AND you have a single 512 Mb or 1 Gb module in the machine now, you may want to seek out a matching module. But trust me, don't bother.