Thanks for your comments and advices.
Finally I ordered yesterday the Braille B2317

Weight 17lbs / 7.7kg
Length 6.8" / 175mm
Width 4" / 102mm
Height 6.1" / 155mm
PCA 1191
CA 770
Ah 23
Reserve capacity 45min

It was a package deal at german epay. Battery, charger, hold down and a kind of tester for 400€ incl shipping
Will take some time till it is in place as I am reworking my whole wiring harness but I will give an update how it works.

cheers
Dennis