any ideas how to fit one to back of arm rest, looked through threads and nothing really I'm looking for. or anyone know the average cost of having garage fit one? thanks...

Morning, I bought this back in Oct from my man Nello and been using it constantly since (how did I ever live without it?), but an imminent PX means it's got to go. I'm not sure what the retail is but I paid £30. Open to sensible offers, but please bear in mind that it'll certainly cost a few...