Does this help, reply from Kung Long for a 1200 battery.
Dear Les,
Thanks for your interest in our products. We think the battery you are using now
is coded 51913.
The equivalent battery type in our program is WP20-12U, which is sold quite
well among our European distributors to replace the originally equipped 51913.
However, ours is a "lead-acid" version instead of the Gel one you prefer. Will
this cause any inconvenience? Below you can the spec. sheet of our WP20-12U
for technical preview. Let us know if you still have any other question.
http://www.klb.com.tw/dbf/WP20-12U.pdf
There's 1 more critical concern about your inquiry as our distributors in UK do
not carry WP20-12U in their programs. I just found 1 who will have a shipment
from us in late January. If you are able to wait till late Feb. ( normally it takes
30 days to ship from Taiwan to UK), you can contact this distributor and ask
whether if they can import some pcs for you. They are located in Marlow Bucks
and we'll advise their contact information after we get their reply.