P11 tyres

Hi.
I dont like the Dunlop P70, i use them on my BSA R3.
I would like to fit:
Front: Heidenau Trials Tyre Universal 325x19;
Rear: Heidenau Trials Tyre K67 400x18.
But i cannot find the rear, is always out of stock!
What tyres do you mount on your P11?.
Thank you.
Piero
http://www.vintagetyres.com/search?sup=23037