I can recommend this one having spent many winter topless miles in it and it's adaptable. Saddle soap ensures it's waterproof.
Currently reduced to £40 from £80 allegedly. No connections other than satisfied customer.
Did the run over from Cambridge to South Devon in January topless in it and felt nice and cosy with no risk of it becoming airborne.
http://www.lakelandleather.co.uk/Lakeland_Newton_Mens_Sheepskin_Cap_in_Brown
