Hello Pignut
Maybe I can help.
If you can track one down thats been done in an agreeable style, I think your mother might like a carved Japanese 'netsuke' Mouse.
Netsuke is a style of Japanese carving that dates back to the 17th Century . Netsuke are small carvings made of wood stone or ivory that were often used as buttons or toggles or worn on clothing. They are very collectable and often really nice pieces of sculpture in their own right. They are also very reasonably priced - unless you are collecting ones dating back to 17th Cenutry!!
I have seen them on sale in Merton Abbey Mills in South London but note you are in Lincolnshire.
You could always try Ebay - there is one listed at the moment
'netsuke' Mouse
But I have seen far nicer designs than this one.
Also should explain the subject dipicted by nutsuke can be anything under the sun - also you should only have to pay between £5 - £12 for a nice modern nutsuke.
And it's sort ot bushcrafty tradtitional craft related ! (especially if they used a crook knife!)
Good luck in your search
Kind regards
Paul