Acquiring Sneak Attack

[Windstorm]

while working on a backup character for a current campaign, I ran into an interesting conundrum that searching isn't yeilding any answers for.

current build on the character is crusader 1/wiz 3/ruathar 3/spellsword 1/abjurant champion 4 (total ECL 12) and I am currently trying to figure out a way to semi-permanently gain sneak attack for the purposes of qualifying for spellwarp sniper, however I would like not to lose a caster level in the process (thus why rogue and ninja dips are a problem).
allowed sources are any 3.5 non-setting material including web.

it might just be a bad case of not enough sleep, but I'm drawing complete blanks.

[nedz]

Unseen Seer isn't going to do it, it just adds a dice to any sneak you already have.

There is an ACF chaining option, but this kind of depends upon your DM
Wizard—Combat Wizard (UA, p 59)—gives you a Fighter feat—Stealthy (UA, p 58)—Sneak attack.

[Bakkan]

Spending a feat on Martial Study(some shadow hand maneuver) and Martial Stance(Assassin's Stance) will give you 2d6 sneak attack as a stance. Check with your DM to see if this qualifies you for things requiring the sneak attack class feature.