Core only, nothing you can do.
But I've looked at the Healer before and noticed that right up until 20th level, it actually gets more spells per day than the Cleric, though drawn from a less than impressive spell list. So the way to get around that is to PrC out into classes that grant you spells that you do want to cast.
If you were playing in Eberron, I'd say go to the crazy extreme just to spite them: Start in Healer, bounce into Divine Oracle at 7th 6th to pick up a domain (Oracle, obviously), which qualifies you for Sovereign Speaker. Take levels in that to pick up domain after domain after domain. Once you have the Good domain which contains Dispel evil, you qualify for Sacred Exorcist, which grants turn undead, and potentially opens up divine metamagic cheese. You'd unfortunately lose 1 caster level at Sovereign Speaker 1, and I've not looked closely enough to see whether the feat requirements for each of these PrCs can be met, but it sure would be fun to turn the Healer into a cleric with class features!
Edit: yes, it looks as though Healer 5 / Divine Oracle 1 / Sovereign Speaker 4 / Sacred Exorcist 1 / Sovereign Speaker 1 / (Contemplative 6? / Divine Oracle 1 - and finish off with Healer 6 just to thumb your nose - it's +1 BAB and +1 to all saves, after all) works fine. There's a throwaway feat needed for Sovereign Speaker, but otherwise there's plenty of space for divine metamagic feats, or domain spontaneity feats, and Extra Turning. You could easily have 8 domains (Oracle, Good, four more from a wide range and two completely free choices from Contemplative) and could squeeze a few more in with dipping in other classes. Ends with CL 19, one fewer 9th level spell but one more 6th level than a Cleric 20, and a Will save through the roof.