It might just be the circles I run in, but adventure crossovers for Goku and Bulma always feel a bit rare compared to pure romance fics or straight DBZ action stories. There's this one series on AO3 by a user named BlackRockChaser that crossed 'Dragon Ball' with 'Indiana Jones', where they're essentially relic hunters tracking down the Dragon Balls before Frieza's forces can misuse them. The author really nailed Bulma's tech genius translating to decoding ancient traps, and Goku's pure strength solving puzzles in the most brute-force, hilarious ways.
Archive of Our Own is your strongest starting point, no contest. Their tagging system is a lifesaver. You'd want to search within the 'Dragon Ball' fandom, filter by the Goku/Bulma pairing tag, and then add additional fandom tags for the crossover you're craving. Using 'Adventure' as an additional character or freeform tag helps too. Sometimes the best stories aren't tagged as crossovers but just borrow the vibe, so I'd sort by kudos and dig through the summaries of longer fics.
FF.net has a massive archive, but its organization is a nightmare from a bygone era. You'd have to go to the Anime/Manga section, find the 'Dragon Ball Z' category, then the 'Goku x Bulma' sub-category, and then just... scroll forever, hoping a crossover summary catches your eye. I've found a few gems set in the 'Uncharted' universe there, buried under mountains of high school AUs. Tumblr can be surprisingly good for recs if you follow blogs that curate niche pairings, but actually finding the complete fic on there is always a gamble.
Honestly, the thirst for that specific combo probably comes from the show itself. They had the original adventure, right? Before all the galactic god-level threats. So seeing them plopped into another universe's high-stakes exploration scenario just feels like returning to the show's roots, but with a fresh coat of paint. The dynamic writes itself: Bulma's brain, Goku's brawn, and a whole new world to get hilariously lost in.
I've had better luck searching for crossovers that focus on the adventure genre itself, like 'Tomb Raider' or 'Journey to the West' inspired stuff, rather than specific series names. Sometimes authors are more into the trope than the exact franchise, and those stories can capture the spirit perfectly without getting bogged down in rigid canon from two different worlds. The ones that treat it like a buddy-cop movie across dimensions are usually the most fun reads.