If you want a strap that is 3/4" or less, that's tricky as the usual width is more along the lines of an inch to 1-1/8". 

Brooks Brothers always has straps.
http://www.brooksbrothers.com/IWCatProductPage.process?Merchant_Id=1&Section_Id=460&Parent_id=1032&Product_Id=983531&default_color=Black

It may be worthwhile to ask around at better shoe repair places, as a real cobbler should be able to help.

As seen in the Brooks link, straps with a snap can be quickly changed, so the same buckle gets as many straps as you want.  Short answer is to match shoes.