Tootall makes a good point. To give you the best referral for a strapmaker it is important to know what you're looking for. Lead time, customer service, price point, quality, desired look, reputation, prestige, etc.
I, for one, want a reasonable lead time, pleasant service, and will pay a premium for quality.
Some makers have 10+ week lead times. Is this important? Ask the maker before ordering.
I've dealt with strap-makers that are not polite, not polite at all. One maker, APBands, has been so difficult to deal with that I will no longer order from them, despite their offering of quality goods.
Below is a list of makers, some have been mentioned here, some not that tend to make high-quality straps:
1. Di Stefano
2. Rob Montana (excellent CONUS based maker, very friendly)
3. Toshi (GB based, decent price, nice goods)
4. Ted Su
5. Kevin Ammo
6. Vintager Watch Straps AKA Micah (CONUS based)
7. Greg Stevens Design
8. Atelier du Bracelet Parisien AKA ABP (Very expensive)
9. Wotancraft
10. David Lane
11. Altamarea Straps (great gator straps but they have a range)
12. Peter.watchacc Straps (nubuck alligator straps)