There's no law against the general public owning a magazine parts kit. If the seller disassembles the mags before you take possession, they are legal. Just don't reassemble the parts while in the state.
You could keep the parts kits for use when you travel to other states, assuming you wish to carry there. Buy a compliant set of 10 rd mags and use those here for practice, home defense, etc.
Parts kits .... just parts kits .... they don't hold any rounds with taken apart.

Having an FFL take possession of the standard capacity mags, if the gun is sold with them, is the legally recommended route for assembled mags. They can block them for you, but that costs almost as much, if not more than, a compliant replacement mag.
I usually try to buy the compliant mags with the gun if possible. Some buyers are so determined to buy a given gun, they will, however, ask the seller to keep the mags and just sell them the firearm.
So many ways to skin this cat.