Part Number for XL Strap for Mark XVIII

Is there a reference number for the XL Santoni calfskin strap in black for the XVIII? Also, is there a depolyant available from IWC with the correct brushed finish that I could pair with the new strap? I measure the buckle ID at 17mm which is a little strange, I think. 18mm seems more typical.

I picked up a Mark XVIII for myself a couple weeks ago when I was travelling and I am really enjoying the watch but I am wearing the strap in the second to last hole which isn't ideal and I do prefer a depolyant with leather vs a pin buckle even if slightly incorrect with this watch. I tried in various ADs and boutiques across Europe to get the XL strap but none had it in stock yet.

a pic from a few days after I bought the watch!

Hi LEFTNOSE,
Strap ref: IWE06164
Folding Buckle for Big Pilots Watch (18mm) IWA05337
Wishing you many happy years with your new IWC,
Leo

Thank you!

I just got an email from an IWC boutique regarding availability of the XL strap. I had asked them about the strap before I made the original post above and they offered to keep me informed when they arrived.

However, they refer to the XL strap as the IWE06167 vs the 06164 number provided above. Now I am wondering which is correct?

Thanks.