the only vendor I know that does 21mm mesh straps is watchgecko:Hi guys, I'm looking for a great quality mesh bracelet (shark mesh or "normal" one) preferably in matte finish, any recommendations? (it seems impossible to find in 21mm size nowdays😪😪)
Stainless Steel Milanese Mesh Watch Strap. High Quality. Choice of size and colour. Polished or satin stainless steel, IP PVD black or gold plated finish.
Unfortunately, it’s only being produced in polished format.
also try this link where a user places a 22 shark mesh on the 300:
I have purchased the Alpina Seastrong Heritage and would like to fit a shark mesh strap to it. Unfortunately this watch has a lug width of 21mm and I' m struggling to find a strap with the correct width. Most likely a 22mm strap will fit, but I would really like to see pictures on how it looks...