Stihl offers this lawn mower that can hold 30 litres of grass in its collection box. A maximum cutting height of 65 mm is suitable if you like medium high grass.
From OnBuy
Stihl RMA 235 Cordless Lawn Mower
Sims Garden Machinery
STIHL RMA 235 13″ Push Cordless Lawn Mower (TOOL ONLY)
Downtown
Stihl RMA 235.0 Cordless/Battery Push Rotary Lawnmower - SHELL ONLY