You have no chance of getting one from a caravans breakers.I have been looking into Hobby breakers for the last 10 years and it's a waste of time and effort..if you look on ebay parts for Hobby's do appear usually sold by sellers called...waynevanman and blackpoolebelle123..However you may see full caravans sold by either Lowe caravans, pickett2005 and sometimes Freddyjohn, they all operate out of Ingatestone in Essex and although they do not actually advertise spares, if you contact them they may well have what you want...The RM 4270 was in common use from around 1997 to about 2000..If i come a cross one i will let you know
Cheers
Hobbynut
The website for Hobby UK is
http://www.hobbycaravansuk.co.uk/
Don't even ask the price unless you are sitting down and want a cardiac arrest of the wallet