Actually, the flapped type of holster sold by Pacific (and others) is the type which would have been used by a
commissioned officer, who was required to supply all of his own kit (including his revolver and holster) at personal expense .... and who, in any event, was more likely than not to have some revolver
other than a Webley Mark I.
Strictly speaking, the "Mark I" designation identifies the revolver as being an approved model owned by the War Department, for
issue to Other Ranks. (Admittedly, the same model
could be purchased privately directly from Webley, but officers were more prone to acquire a different model entirely, such as a Webley-Pryse, or W.G. Army.)
If your revolver has WD markings, then the
correct revolver case (War Department term for holster) for it would actually be the open top version first introduced by the War Department in 1877 (a decade prior to adoption of the Mark I Webley revolver) for issue to any Other Ranks deemed to require a revolver .... It should look pretty much like this one - a Mark II, with the loop on the back introduced in December 1896 (and which was to be added to existing cases, as well as incorporated in all subsequent manufacture .....)
As you can see from the photos (and material added below) in the absence of the flap, and with no "toe plug" in the body of the holster, this would be a fairly easy piece of kit to make. If you lack leather-crafting skills or facilities, this type of holster is also available from various suppliers who cater to WWI re-enactors, although admittedly their versions tend to be the somewhat later configurations made to fit Pattern 1903 Equipment (and later Patterns also used in WWI, such as P'08 and P'14) and usually are made long enough to accommodate the 6" barrel of a Mark VI Webley. (However, the simple construction, without toe-plug, permits the holster to be shortened quite easily, if one desires .....)
Here are the three versions offered by "What Price Glory" US$36 each, including replica brass cleaning rod) . These are left "unfinished" so they can be dyed to suit the purchaser, or left to acquire the appropriate tone and patina from use and oiling ....
And this one is offered by Schipperfabrik for US$44.95 (shown with an Other Ranks-pattern cartridge pouch they also sell for US$34.95). They only offer the P'1914 version ....
And now, for those prone to say "show me" or those who appreciate "primary source" documentation, here are some relevant entries in the British War Department's "List of Changes" (only the last of these was "illustrated", but I have highlighted the description in the first one) -
Finally, a nice photograph showing both types of holster in use - commissioned officer on the left, non-commissioned officers on the right -
