Contact a main Yamaha dealer. Some 2-strokes were available with front mounted gear shift, Such as a 40hp, such as 2 stroke non-Enduro model 40V (6H4). Your Enduro engine will be either E25BMHL (long-shaft) or E25BMHS (short). If it's new then expect to pay £350 easily from Yamaha.
Is that with or without VAT?