I have a set of these Rapala scales on board.
https://www.rapala.co.uk/uk_en/25-kg-proguide-digital-scale
They are compact and accurately weigh my fish heavier than the ones @Andy135 catches. So very reliable in my book!
@Geoff look at what garmin unit you want and I'll get you a terrific discount.
Just ask @JonC and @daio web!!
Will be a hell of a lot cheaper than a raymarine.