Zefal Deflector RS75 Rear Mudguard

After market rear mudguard that fits well onto most bikes and strikes a good balance between coverage and stability. A good choice if your e-bike didn't come with full fitting mudguards and you want to take the edge off riding on wet days. Also keeps the bike low fuss when doing things like packing up your bike for travel. A corresponding front mudguard is available. 

From the manufacturer:

Zefal Deflector RS75 Rear Mudguard
The Deflector RS75 provides solid protection for all mountain bikes. Through its unique, close-to-the-wheel mounting, it is both unobtrusive and undoubtedly effective. With its suspension arm mounting, the RS75 works on all types of suspension bikes. 

Features

• Fits 27.5" and 29" bikes
• Fits maximum tyre width 2.8''
• Universal fitting
• Supplied with instructions
• Full suspension ready
• Mounts to rear stays - Adjustable from 16mm to 42mm
• Blade width is 81mm at it's narrowest and 92mm at it's widest
• 585mm long
• Fibre-glass reinforced polypropylene
• 341g
• E-Bike compatible