Unlike uncanny dodge, evasion doesn't automatically upgrade to the improved version if you get it twice. Looking into ways to acquire improved evasion, you might be best served by ninja spy (Oriental Adventures, p43). That gives you improved evasion at 2nd level. If you stay for 3rd level, you get +10 on balance, climb, jump, and tumble checks, plus the ability to take 10 on said checks during combat. If you stay for the 4th level, you get hide in plain sight, which could replace shadow dancer and save you from having to take mobility.
An alternative to improved uncanny dodge is rudimentary eyespots (Lords of Madness, p216). They do check in at a substantial 60,000 gp though. Grafts, if your not aware, are extraordinary after they've been installed on your body.
There actually already is a rod that shoots the equivalent of a tanglefoot bag. It's rod of viscid globs (Magic Item Compendium, p176). It only works 3 times per day though. The older version from Magic of Faerun worked 5 times a day, but cost more.
I don't think there's any item that grants immunity to surprise, but I did remember another way to get it. The mark of stars feat (Dragonmarked, p142) has the benefit "You are never surprised or flat-footed." Unfortunately, it requires a Siberys dragonmark. As far as I know, the only way to get one is to take 2 levels in the heir of Siberys prestige class, which itself requires 15 ranks each in 2 skills. You could go stuff 12 / heir of Siberys 2 and take the feat at 15th level, which is actually the earliest the other immunity-to-surprise abilities can be acquired anyway.
Never being flat-footed is actually much better than just retaining your dexterity bonus to AC when flat-footed. You can't take immediate actions while flat-footed, and you're automatically flat-footed at the start of combat until your turn comes up. With mark of stars, it's possible to use immediate-action abilities to respond to things before your first turn.
