Hi Paddy,
Happy New Year to you as well. I've not seen any "finasteride" based shampoos specifically but there are a load of hair loss fighting shampoos. I've been using GrowMD for a few months now, the one that Spex is promoting, and while I can't say if it is doing anything regarding DHT, I do like it in general. My interest in this product has more to do with some users claiming it reverses graying hair. So far, I MIGHT be seeing such developments for myself, but it is difficult to say at this point. My wife is cautiously in agreement with me. As a disclaimer, I have no professional or financial affiliation with GrowMD.