'Hawaii Five-0' Star Paige Hurd -- I Want to Buy that Dog You're Walking!

"Hawaii Five-0" star Paige Hurd wants what she wants when she wants it ... and that goes for random dogs she sees on the street.

Paige was walking near the Staples Center in L.A. Sunday when she saw a guy walking a 3-month-old female Bullmastiff.

She started fawning over the pooch and one thing led to another -- he said he had a whole litter at home -- and suddenly it became a transaction. Paige agreed to pay $700 on the spot for the pup.

Problem #1... she didn't have the money, so Paige ran to an ATM. Problem #2 ... she could only withdraw $500, so a family member fronted her the balance.

So Roxxie Redd -- formerly known as Barbie -- is now part of the Hurd.