A custom ritual based on the Ritual of Transfiguration
Savage Species has the Ritual of Transfiguration on page 149 as a way of adding incorporeality to a character. It adds the incorporeal subtype rather than remove it, but it's worth looking at. It's even worth perusing the whole section on rituals in Savage Species with the caveat that SS has a lot of fun ideas, but pretty poor implementation. It's also 3.0, so some things (like the type pyramid) were overwritten by 3.5 rules. The rituals, however, still function perfectly well in 3.5.
The Ritual of Transfiguration requires 306,000 gold and, bafflingly, a level 17 or higher cleric with the Animal domain. I find the Ritual of Transfiguration to be extremely silly in the particulars—it's wildly over-costed and I don't understand what the Animal domain has to do with incorporeality—but it's a starting point for paying X amount of gold to a specialized spellcaster to remove your subtype.
I genuinely think that this is the best route to go: some sort of ritual of incarnation that gives you a corporeal body. Maybe you need to find a cleric with access to the Renewal domain (from Spell Compendium) or the Transformation domain (from Races of Eberron) or, in your case, the Dream domain (SC). How easy it is to find such a spellcaster and how much it costs are levers that your DM can adjust depending on whether they want this to be a major plot point, a quick sidequest, or a simple task next time the party has downtime. As for how much gold it should cost, you're mechanically making your character worse in most respects, so I wouldn't put this much past 3 – 5,000 gp. The upside of such an effect is rather like the feat Ghostly Grasp (from Libris Mortis), and perusing the items that mimic feats in this list puts such effects between 3 – 10k, and I'd say this is on the weaker side of that spectrum.
Changing species entirely
But if, for one reason or another, you'd rather not homebrew anything, an easy way to do this would be to get a druid to cast reincarnate on you after you die. This will, of course, remove all your racial traits, which might be problematic, but it's an official way to permanently get rid of the incorporeal subtype. If you have access to it, wish can change your species (as per Savage Species 150), but that's a very high level option. If you do have access to 9th level spells but not wish specifically, true reincarnate from Masters of the Wild is a great option, giving you a bit more control over what you come back as, and preventing the level loss of regular reincarnate.
Risen Martyr?
Lastly, there's the risen martyr, from Book of Exalted Deeds, which explicitly gains a "corporeal spirit form" upon entry into the class (which has a 0th level). It doesn't remove the incorporeal subtype, but is arguably more specific a rule than the incorporeal subtype always making one incorporeal. It's a campaign-warping class, though, more so than even other exalted material. But if the whole party is on board for a New Testament sort of campaign, it probably gives you a corporeal form.
