Since it has been a discussion here and several other places without any clear answers, I though I would share my findings with other PT911 owners.
When it comes to holsters for the PT911 and PT908, I have found very little information on the web, and what I did find was confusing.
I have been able to find more generic, soft holsters that fit my PT911 reasonably well, but wanted to find a kydex/plastic style that had better fit and a little more retention. The holster companies are a little confusing about fit when it comes to this pistol. I tried the Sig228 as some have suggested, but its just not the right fit.
The PT908, PT911, and PT940 have the same relative trigger guard and barrel dimensions for holster fit. I purchased a Fobus Roto PT940 model and it fit perfectly.
Though I have to say that there is not alot of options when it comes to styles of 940 holster, as there are other models of pistols. There may be more out there, but it seems to be slim-pickins. However, I am happy with the one I purchased.
The PT945 also shares most of these dimensions, but has longer frame and barrel. So a PT945 holster should fit the 908/911/940 if it is a short open-bottom style. I admittedly have not actually tried this type of holster, but in comparing the weapons dimensions and profiles, I am pretty sure it would work. If you got an execptional deal on a 945 holster I might try it, otherwise look at a holster for a PT940 model. Although you may be able to find more options and variety with a 945 holster.