JR makes great Lange straps. Best experience is if you visit their NYC boutique twice -- first to pick your skin (by the window, in natural lighting) and get measured, and second to pick up the strap and have them punch the holes in it (if you trust them to put the strap on your watch while you're there). I get 2 holes punched, for warm vs. cold weather wear. I also get only 1 keeper (vs. 2 keepers) because the second keeper is unnecessary if the strap's tail is the correct length (not too long).
Here's an (older) JR order for a strap that fits a Lange 1 with a deployant buckle to my 6"/154mm wrist -- shows you the padding spec, etc. -- and the importance of specifying the round tip ("ALS") rather than the pointed tip:

This grey strap is the lower one in this pic; the top strap is same dimensions but different skin/stitching:
Here they are on watches:
Here's the front and back of another JR strap, if you want to see what back looks like with alligator lining specified:
I've also ordered from Hadley Roma. HR straps, like JR's custom straps, are made in the US so you're not dealing with import/Customs issues. I haven't ordered from HR in years, though. I really liked HR straps, and they were far cheaper than all the others. I ordered the "Alligator 2005" series:
These were the specs that I used to give Hadley Roma when I wanted a custom Lange strap made like the ones just above:
(1) Material: Alligator or Crocodile (Alligator 2005 Series is best)
(2) Grain: Wide/bamboo tiles, not small/random scales/tiles
(3) Color: Chestnut or Cognac (NOT dark chocolate brown)
(4) Finish: Matte or Semi-Gloss (NOT high-gloss)
(5) Length: 52mm x 111mm
(6) Width: 20mm (lugs) x 16mm (buckle)
(7) Tip shape: Rounded/boxed tip on long end, not pointed