If injected plastic is ok look at the Fobus SG 21.
Used my 5906 with square trigger guard at a tactical shooting session today. The holster is made for the 5906 as well as the SIG 226. Look at a picture of the SIG and you will see that it too has a similar trigger guard shape. I have the OWB model. Holds gun securely but easy draw. It does have about a 30 degree forward slant. I know some do not think much of Fobus but the QWB seems ok.
After over 50 draws, I can not see any wear mark on the 5906
Price seems OK too, around $30.
Lobogunleather; ur site says round trigger guard for 5906, how about us "squares"