Produced by different manufacturers, you can choose which one you want (or any).
ACORN BBC MASTER 128 NEW REPLACEMENT LITHIUM LONG LIFE CMOS RTC BATTERY PACK
ACORN BBC MASTER 128 - FULL ELECTROLYTIC AND X2 CAP KIT FOR ACORN & HITRON PSU
ACORN BBC MASTER 128 MULTI OS 4 OS IN ONE - 1.20, 2.00, 3.20 AND 3.50 - FOR IDE
ACORN BBC MASTER 128 NEW REPLACEMENT 3AA CMOS RTC BATTERY PACK HOLDER & CABLE
Vintage Acorn BBC Master 128 Computer with Econet, MMFS and User Port Switch
ACORN BBC MASTER 128 - INTERNAL RASPBERRY PI ZERO CO-PROCESSOR ADAPTER BOARD
