I have ordered seeds from ILGM before and had great success. Not specifically Durban Poison Auto but they have great seeds. Humboldt and Blimburn also have them and are very reputable. Auto Seeds has them as well. I've grown some of their seeds in the past with good success.
You can likely find a cross, but unless it's been heavily worked for stability, it's not going to be ruderalis Durban poison, it will be an f1 of an unnamed autoflower and DP.