3E is dead to wizards, there will never be an official response. Maybe if you ask Monte Cook or another former big time player from the 3E era that no longer works there, you can get a "very, very, very close to official but yet still not quite" answer.
The most inexpensive way to get the spells you need if there's no cooperative-minded friend is to just take the Leadership feat at level 6 and provide one for yourself. Really, Leadership is the answer to just about all of D&D's problems.
Again though, even with a caster, get UMD ranks, get items. Still useful to get SA, use as a plan B when you can't SA, and even to combine with SA. Any spell that does damage and requires an attack roll (and can thus always hit on a 20 or miss on a 1) lets you add sneak attac damage to it, of the same energy type. So a wand of say...acid splash...is pretty dangerous in your hands. d3 + Xd6 acid damage that's hitting flatfooted touch AC (hint: unless it's a monk, this is going to be 10-15 at the most generally) and allowing no spell resistance. Any cold damage, even the weak ray of frost, does +50% to fire subtype creatures. Doing 50 damage to a red dragon with a cantrip just
feels awesome.
Seriously though, if he's going to screw you out of sneak attack in any form of concealment even with seeking or IPS, don't make a rogue. Whether a rogue can sneak attack is already wildly dependent on DM fiat (picking enemies immune or not immune to it), letting him have the option of MANY low level spells and effects that neuter you just makes matters far worse.