Dianna - here's a couple of suggestions for you
1/ Screening a dog walker - basically you're hiring someone to come into your home, so screen them like you would anyone else. Here's some pointers
a) Do they have references?
b) Are they comfortable around your pets? Do they look like they know
what they're doing?
c) Do they own pets of their own? For how long?
d) Are your pets comfortable around them?
e) What services do they offer? How long will they walk the dog?
You're a pet owner, so you'll have a pretty quick sense of how your pet is around this new person. Spend some time w/ them in your house and w/ the pet.
2/ Pet sitting company -
www.wishyouwereherehk.com. They do dog/cat-sitting, & may be able to help. I used them very regularly for my own cats for past 2 years. The English guy is a dog-trainer as well.
3/ Networking - you can talk to Hong Kong Dog Rescue
www.hongkongdogrescue.dog. I know a couple of people there do dog walking outside the center. They can circulate your request around.