Our sources tell us Kylie threw down a cool $12,000 for a custom Beanie Baby bear covered in crystals ... this after seeing the piece at Justin and Hailey Bieber's Paddle 8 auction.

The super rare Beanie Baby is designed by Los Angeles-based artist Dan Life, and it's 1 of only 5 ever created. Dan's known for his nostalgic works inspired by his 90s childhood -- he makes a lot of flashy Pokemon art as well -- and this bear is his twist on the classic Erin Beanie Baby from back in the day.

We're told Dan already dropped the bear off with Justin, and the Biebs is gonna hand-deliver it to Kylie!

Sure, it's a lot of money to spend on a toy Stormi will never get to play with ... but the money raised from Justin and Hailey's auction benefits needy families in L.A. ... so Kylie's supporting a good cause.