First, you might want to check if the fluff requirements here are being enforced at all. Tome of Battle offers an official adaptation section suggesting ruby knight vindicators of other deities would make sense and shouldn’t be a problem, and the restriction on LN Wee Jas clerics always using rebuke/inflict instead of turn/cure is pretty obscure and rarely noticed, much less used. So you may not actually have to worship Wee Jas, and may not actually have to choose rebuke/inflict even if you do. But if your game is enforcing those, or you would prefer for your character to do so even if he doesn’t have to, read on.
Second, note that burning spell slots on cure spells, while certainly better than inflict spells, isn’t really that great a choice much of the time (for all clerics, not just ruby knight vindicators—they seemed to consciously account for the cleric’s spontaneous casting by making those spells weaker). In the middle of the day, you are probably better off saving whatever you prepared, and zapping a wand of cure light wounds or lesser vigor between battles. These wands are 750 gp, which means a party can, and should, pool their wealth to buy one even before reaching 2nd level. By the time you finish its 50 charges, a second will be quite affordable, and by the time you need a third it will be chump change. And if you do that, spontaneous inflict is much less of a downside. But you’ll still go to bed with some spells uncast—arguably a good thing, in case you get attacked in the night, but if you feel it’s inefficient, well, read on.
Third, finally, there are options for different spontaneous casting on a cleric. The most straightforward is the spontaneous domain casting alternate class feature from Player’s Handbook II—instead of spontaneously casting cure or inflict, you spontaneously cast spells from one of your domains. The Domain Spontaneity feat from Complete Champion is similar, though you have to burn turn/rebuke uses on it. Most similar to a runestaff is a domain staff from Complete Champion, but it only lets you swap in each spell in the domain once per day (similar to how you only have one domain slot per spell level). A domain icon from Faiths of Eberron lets you spontaneously swap a spell for a spell from that domain 3/day; you don’t even need to have the domain, just be of an appropriate faith. For that matter, a domain draught from Magic Item Compendium can get you any domain for 24 hours.