Create anchoring foci (maybe in a bound free spirit sweat shop) with simple triggers a mundane can activate. The corporation has a bound free spirit casting the spells, so every time the anchor gets activated, the free spirit ignores the Drain. The mundane buying the focus still needs to pay karma as though they are bonding the focus, likely 2-3 times the rate a mage would need to pay. An appointment is set up to get the focus and pay the karma for it. Have someone magically active on hand to try to increase the ratio of the karma exchange. Have the enchanting free spirit on hand to get their karma recharged so they can start working on the next focus.

Whew, thought you were gonna instead have a Spook backed Corp dump a load of Imp Infested Foci who have devised a way to drain Karma from mundanes to fuel their wacky foci shenanigans.