Measurements of designer button down shirts sought

[learnerofgerman]

I'm a size 16 (neck), 36 (sleeve length), which precludes me from buying most designer shirts off the shelf. I'd love to be able to buy something and have it tailored later, but b/c sleeve lengths for size 16 shirts are generally 34/35, I'm out of luck.

I'm curious if anyone out there has the standard measurements of designer shirts from places like Banana Republic, JCrew, Gap, etc. to name a few.

I'm looking for specifics like sleeve length, neck size, shirt length, chest, waist, etc. for the shirts sold in the store. If you ask the clerk, he/she sometimes has those measurements, but I haven't been in one of these stores in a while.

Thanks!

P.S. I'm also looking for a good source of custom tailored shirts online if you can suggest one.