This lithium battery from JMT type HJTX20CH-FP is rather small and will fit perfectly on your Chopper!
Dimensions: 150 x 87 x 105 mm

Specifications:

Voltage: 12v
Capacity: 6 Ah (10 Std)
Capacity: 72 Wh
Type: Lithium
Maintenance-free
Manufacturer claimed CCA: 360 A
SAE as measured by JMP battery tester: 545 A
DIN as measured by JMP battery tester: 510 A
EN as measured by JMP battery tester: 300 A
Length: 150 mm
Width: 87 mm
Height: 105, 122, 130, 139, 147, 164 mm
Weight (including acid): 1,19 kg
Terminal connection: Front from above
Positive terminal: front left
Negative terminal: front right
Ventilation hose: none
Manufacturer: JMT

Fits the following:

Ducati 907 900 ie 1990 2 90 BHP, 66 kw
Ducati 907 900 ie 1991 2 90 BHP, 66 kw
Ducati 907 900 ie 1992 2 90 BHP, 66 kw
Ducati 907 900 ie 1993 2 78 BHP, 57 kw
Honda VF 1000 RE
Honda VF 1000 RF
Honda VF 1000 RG
Honda VF 1000 F2 Bol d'Or F
Honda VF 1000 F onderschepper
Honda XL 1000 V Varadero 3
Honda XL 1000 V Varadero 4
Honda XL 1000 V Varadero 7
Honda XL 1000 V Varadero 8
Honda XL 1000 V Varadero 9
Honda XL 1000 V Varadero A
Honda XL 1000 V Varadero 3
Honda XL 1000 V Varadero 4
Honda XL 1000 V Varadero 5
Honda XL 1000 V Varadero 6
Honda XL 1000 V Varadero B
Honda XL 1000 VA Varadero ABS 4
Honda XL 1000 VA Varadero ABS 5
Honda XL 1000 VA Varadero ABS 6
Honda XL 1000 VA Varadero ABS 7
Honda XL 1000 VA Varadero ABS 8
Honda XL 1000 VA Varadero ABS 9